diff --git a/gpx-rs/engine/src/engine/command/edit/metadata.rs b/gpx-rs/engine/src/engine/command/edit/metadata.rs
index 0b88bba06..4009d1cc0 100644
--- a/gpx-rs/engine/src/engine/command/edit/metadata.rs
+++ b/gpx-rs/engine/src/engine/command/edit/metadata.rs
@@ -17,6 +17,10 @@ impl Editor for Metadata<'_> {
     fn file(&mut self, file: &mut File) -> Edit {
         file.info.name = self.name.to_owned();
         file.info.desc = Some(self.desc.to_owned());
+        // a single track is named like the file
+        if let [track] = file.trk.as_mut_slice() {
+            track.info.name = Some(self.name.to_owned());
+        }
         Edit::Changed
     }
 
@@ -31,7 +35,7 @@ impl Editor for Metadata<'_> {
 mod tests {
     use std::collections::HashSet;
 
-    use crate::{New, Selection, engine::command::fixture::Fixture};
+    use crate::{New, NewTrack, Selection, engine::command::fixture::Fixture};
 
     use super::*;
 
@@ -83,4 +87,55 @@ mod tests {
         assert_eq!(after.trk[0].info.name.as_deref(), Some("renamed"));
         assert_eq!(after.trk[1].info, file.trk[1].info);
     }
+
+    /// A new file with `nb_tracks` tracks (without name), selected.
+    fn file_with_tracks(fx: &mut Fixture, nb_tracks: usize) {
+        New { name: "file" }.apply(&mut fx.state()).unwrap();
+        for _ in 0..nb_tracks {
+            NewTrack.apply(&mut fx.state()).unwrap();
+        }
+    }
+
+    fn rename(fx: &mut Fixture) {
+        Metadata {
+            name: "renamed",
+            desc: "",
+        }
+        .apply(&mut fx.state())
+        .unwrap();
+    }
+
+    #[test]
+    fn test_single_track_is_renamed_like_the_file() {
+        let mut fx = Fixture::default();
+        file_with_tracks(&mut fx, 1);
+        rename(&mut fx);
+        let file = fx.files.values().next().unwrap();
+        assert_eq!(file.info.name, "renamed");
+        assert_eq!(file.trk[0].info.name.as_deref(), Some("renamed"));
+    }
+
+    #[test]
+    fn test_single_track_with_a_name_is_renamed_too() {
+        let mut fx = Fixture::default();
+        file_with_tracks(&mut fx, 1);
+        let id = *fx.files.keys().next().unwrap();
+        std::rc::Rc::make_mut(fx.files.get_mut(&id).unwrap()).trk[0]
+            .info
+            .name = Some("track".to_owned());
+        rename(&mut fx);
+        let file = &fx.files[&id];
+        assert_eq!(file.info.name, "renamed");
+        assert_eq!(file.trk[0].info.name.as_deref(), Some("renamed"));
+    }
+
+    #[test]
+    fn test_several_tracks_are_not_renamed() {
+        let mut fx = Fixture::default();
+        file_with_tracks(&mut fx, 2);
+        rename(&mut fx);
+        let file = fx.files.values().next().unwrap();
+        assert_eq!(file.info.name, "renamed");
+        assert!(file.trk.iter().all(|trk| trk.info.name.is_none()));
+    }
 }
diff --git a/gpx-rs/engine/src/engine/derived/file_structure.rs b/gpx-rs/engine/src/engine/derived/file_structure.rs
index 98ebd6426..613ab4214 100644
--- a/gpx-rs/engine/src/engine/derived/file_structure.rs
+++ b/gpx-rs/engine/src/engine/derived/file_structure.rs
@@ -12,6 +12,7 @@ use crate::{
 pub struct FileStructure {
     pub id: FileId,
     pub name: String,
+    pub desc: Option<String>,
     pub tracks: Vec<TrackNode>,
     pub waypoints: Vec<WaypointNode>,
     /// Changes whenever the waypoints of the file (hence their buffer) change.
@@ -22,6 +23,7 @@ pub struct FileStructure {
 pub struct TrackNode {
     pub id: TrackId,
     pub name: Option<String>,
+    pub desc: Option<String>,
     /// Style of the track, only when the file defines it.
     pub color: Option<String>,
     pub opacity: Option<f64>,
@@ -49,12 +51,14 @@ impl FileStructure {
         Self {
             id: file.id,
             name: file.info.name.clone(),
+            desc: file.info.desc.clone(),
             tracks: file
                 .trk
                 .iter()
                 .map(|trk| TrackNode {
                     id: trk.id,
                     name: trk.info.name.clone(),
+                    desc: trk.info.desc.clone(),
                     color: trk.info.color.clone(),
                     opacity: trk.info.opacity,
                     width: trk.info.width,
@@ -99,10 +103,13 @@ mod tests {
         Load { data: &data }.apply(&mut fx.state()).unwrap();
         let file = &fx.files[&fx.order.0[0]];
         let node = FileStructure::new(file);
-        assert_eq!((node.id, &node.name), (file.id, &file.info.name));
+        assert_eq!(
+            (node.id, &node.name, &node.desc),
+            (file.id, &file.info.name, &file.info.desc)
+        );
         assert_eq!(node.tracks.len(), file.trk.len());
         for (n, t) in node.tracks.iter().zip(&file.trk) {
-            assert_eq!((n.id, &n.name), (t.id, &t.info.name));
+            assert_eq!((n.id, &n.name, &n.desc), (t.id, &t.info.name, &t.info.desc));
             assert_eq!(
                 (&n.color, n.opacity, n.width),
                 (&t.info.color, t.info.opacity, t.info.width)
diff --git a/gpx-rs/wasm/src/lib.rs b/gpx-rs/wasm/src/lib.rs
index 384cf96dc..dff664211 100644
--- a/gpx-rs/wasm/src/lib.rs
+++ b/gpx-rs/wasm/src/lib.rs
@@ -436,6 +436,7 @@ export interface FilesUpdate {
 export interface FileStructure {
     id: string;
     name: string;
+    desc?: string;
     tracks: TrackNode[];
     waypoints: WaypointNode[];
     /** Changes when the waypoints of the file change: refetch their coordinates. */
@@ -463,6 +464,7 @@ export interface FileStatistics {
 export interface TrackNode {
     id: string;
     name?: string;
+    desc?: string;
     /** Style of the track, only present when the file defines it. */
     color?: string;
     opacity?: number;
@@ -520,11 +522,17 @@ fn named_node(id: uuid::Uuid, name: Option<&str>) -> Object {
 
 fn structure_object(file: &engine::FileStructure) -> Object {
     let node = named_node(file.id.0, Some(&file.name));
+    if let Some(desc) = &file.desc {
+        set(&node, "desc", desc.as_str());
+    }
     set(
         &node,
         "tracks",
         array(&file.tracks, |trk| {
             let node = named_node(trk.id.0, trk.name.as_deref());
+            if let Some(desc) = &trk.desc {
+                set(&node, "desc", desc.as_str());
+            }
             if let Some(color) = &trk.color {
                 set(&node, "color", color.as_str());
             }
diff --git a/website/src/lib/all-hidden.ts b/website/src/lib/all-hidden.ts
new file mode 100644
index 000000000..74a42113a
--- /dev/null
+++ b/website/src/lib/all-hidden.ts
@@ -0,0 +1,49 @@
+import { readable } from 'svelte/store';
+import { engine, FileStateCollectionObserver, type FileState, type Selection } from '$lib/engine';
+import { isSelectionHidden } from '$lib/selection-helpers';
+
+/**
+ * Whether all the selected elements are hidden. It follows the selection and, through the
+ * observer of the files, the state of every file (hiding, editing).
+ */
+export const allHidden = readable(false, (set) => {
+    let selection: Selection = { type: 'empty' };
+    const states = new Map<string, FileState>();
+    const unsubscribes = new Map<string, () => void>();
+
+    const update = () => set(isSelectionHidden(selection, states));
+
+    const unsubscribeSelection = engine.selection.subscribe(($selection) => {
+        selection = $selection;
+        update();
+    });
+    const observer = new FileStateCollectionObserver(
+        (files) => {
+            files.forEach((store, fileId) => {
+                unsubscribes.set(
+                    fileId,
+                    store.subscribe(($file) => {
+                        states.set(fileId, $file);
+                        update();
+                    })
+                );
+            });
+        },
+        (fileId) => {
+            unsubscribes.get(fileId)?.();
+            unsubscribes.delete(fileId);
+            states.delete(fileId);
+            update();
+        },
+        () => {
+            unsubscribes.forEach((unsubscribe) => unsubscribe());
+            unsubscribes.clear();
+            states.clear();
+        }
+    );
+
+    return () => {
+        unsubscribeSelection();
+        observer.destroy();
+    };
+});
diff --git a/website/src/lib/components/file-list/FileList.svelte b/website/src/lib/components/file-list/FileList.svelte
index de054baa8..f65e0e893 100644
--- a/website/src/lib/components/file-list/FileList.svelte
+++ b/website/src/lib/components/file-list/FileList.svelte
@@ -1,15 +1,17 @@
 <script lang="ts">
     import { ScrollArea } from '$lib/components/ui/scroll-area/index';
     import * as ContextMenu from '$lib/components/ui/context-menu';
-    import FileListNode from './FileListNode.svelte';
+    import FileListNodeContent from './FileListNodeContent.svelte';
     import { onMount, setContext } from 'svelte';
-    import { ListFileItem, ListLevel, ListRootItem } from './file-list';
+    import { ListLevel } from './file-list';
     import { ClipboardPaste, FileStack, Plus } from '@lucide/svelte';
     import Shortcut from '$lib/components/Shortcut.svelte';
     import { i18n } from '$lib/i18n.svelte';
-    import { fileStateCollection } from '$lib/logic/file-state';
+    import { engine } from '$lib/engine';
+    import { selectedFileIds } from '$lib/selection-helpers';
     import { createFile, pasteSelection } from '$lib/logic/file-actions';
-    import { selection, copied } from '$lib/logic/selection';
+    // TODO the clipboard still works on the previous implementation
+    import { copied } from '$lib/logic/selection';
     import { allowedPastes } from './sortable-file-list';
 
     let {
@@ -27,17 +29,12 @@
     setContext('orientation', orientation);
     setContext('recursive', recursive);
 
+    const { files, selection } = engine;
+
     onMount(() => {
-        if (orientation === 'horizontal') {
-            selection.update(($selection) => {
-                $selection.forEach((item) => {
-                    if (!(item instanceof ListFileItem)) {
-                        $selection.toggle(item);
-                        $selection.set(new ListFileItem(item.getFileId()), true);
-                    }
-                });
-                return $selection;
-            });
+        if (orientation === 'horizontal' && $selection.type !== 'file') {
+            // only files can be selected here
+            engine.select(selectedFileIds($selection));
         }
     });
 </script>
@@ -54,7 +51,7 @@
             : 'flex-row'} {className ?? ''}"
         {style}
     >
-        <FileListNode node={$fileStateCollection} item={new ListRootItem()} />
+        <FileListNodeContent node={null} />
         {#if orientation === 'vertical'}
             <ContextMenu.Root>
                 <ContextMenu.Trigger class="grow" />
@@ -66,8 +63,8 @@
                     </ContextMenu.Item>
                     <ContextMenu.Separator />
                     <ContextMenu.Item
-                        onclick={() => selection.selectAll()}
-                        disabled={$fileStateCollection.size === 0}
+                        onclick={() => engine.selectAll()}
+                        disabled={$files.size === 0}
                     >
                         <FileStack size="16" />
                         {i18n._('menu.select_all')}
diff --git a/website/src/lib/components/file-list/FileListNode.svelte b/website/src/lib/components/file-list/FileListNode.svelte
index 2561a2f72..31c96b02b 100644
--- a/website/src/lib/components/file-list/FileListNode.svelte
+++ b/website/src/lib/components/file-list/FileListNode.svelte
@@ -1,89 +1,93 @@
 <script lang="ts">
-    import {
-        GPXFile,
-        Track,
-        TrackSegment,
-        Waypoint,
-        type AnyGPXTreeElement,
-        type GPXTreeElement,
-    } from 'gpx';
     import { CollapsibleTreeNode } from '$lib/components/collapsible-tree/index';
-    import { type Readable } from 'svelte/store';
     import FileListNodeContent from './FileListNodeContent.svelte';
     import FileListNodeLabel from './FileListNodeLabel.svelte';
     import { getContext } from 'svelte';
-    import {
-        ListFileItem,
-        ListTrackSegmentItem,
-        ListWaypointItem,
-        ListWaypointsItem,
-        type ListItem,
-        type ListTrackItem,
-    } from './file-list';
     import { i18n } from '$lib/i18n.svelte';
     import { settings } from '$lib/logic/settings';
-    import type { GPXFileWithStatistics } from '$lib/logic/statistics-tree';
-    import { selection } from '$lib/logic/selection';
+    import { engine, type FileState } from '$lib/engine';
+    import {
+        elementId,
+        hasSelectionWithin,
+        isSelected,
+        type FileTreeNode,
+    } from '$lib/selection-helpers';
 
     let {
+        fileState,
         node,
-        item,
     }: {
-        node:
-            | Map<string, Readable<GPXFileWithStatistics | undefined>>
-            | GPXTreeElement<AnyGPXTreeElement>
-            | Waypoint[]
-            | Waypoint;
-        item: ListItem;
+        fileState: FileState;
+        node: FileTreeNode;
     } = $props();
 
     let recursive = getContext<boolean>('recursive');
 
     let collapsible: CollapsibleTreeNode | undefined = $state();
 
-    let label = $derived(
-        node instanceof GPXFile && item instanceof ListFileItem
-            ? node.metadata.name
-            : node instanceof Track
-              ? (node.name ?? `${i18n._('gpx.track')} ${(item as ListTrackItem).trackIndex + 1}`)
-              : node instanceof TrackSegment
-                ? `${i18n._('gpx.segment')} ${(item as ListTrackSegmentItem).segmentIndex + 1}`
-                : node instanceof Waypoint
-                  ? (node.name ??
-                    `${i18n._('gpx.waypoint')} ${(item as ListWaypointItem).waypointIndex + 1}`)
-                  : node instanceof GPXFile && item instanceof ListWaypointsItem
-                    ? i18n._('gpx.waypoints')
-                    : ''
-    );
+    let label = $derived.by(() => {
+        const { structure } = fileState;
+        switch (node.type) {
+            case 'file':
+                return structure.name;
+            case 'track': {
+                const trackIndex = structure.tracks.findIndex((t) => t.id === node.trackId);
+                return (
+                    structure.tracks[trackIndex]?.name ?? `${i18n._('gpx.track')} ${trackIndex + 1}`
+                );
+            }
+            case 'segment': {
+                const track = structure.tracks.find((t) => t.id === node.trackId);
+                const segmentIndex =
+                    track?.segments.findIndex((s) => s.id === node.segmentId) ?? -1;
+                return `${i18n._('gpx.segment')} ${segmentIndex + 1}`;
+            }
+            case 'waypoints':
+                return i18n._('gpx.waypoints');
+            case 'waypoint': {
+                const waypointIndex = structure.waypoints.findIndex(
+                    (w) => w.id === node.waypointId
+                );
+                return (
+                    structure.waypoints[waypointIndex]?.name ??
+                    `${i18n._('gpx.waypoint')} ${waypointIndex + 1}`
+                );
+            }
+        }
+    });
+
+    // identifies the node in the tree
+    let id = $derived(elementId(node));
 
     const { treeFileView } = settings;
+    const { selection } = engine;
 
     $effect(() => {
-        if (collapsible && $treeFileView && $selection.hasAnyChildren(item, false)) {
+        // open the node when something below it is selected
+        if (
+            collapsible &&
+            $treeFileView &&
+            hasSelectionWithin($selection, node) &&
+            !isSelected($selection, node)
+        ) {
             collapsible.openNode();
         }
     });
 </script>
 
-{#if node instanceof Map}
-    <FileListNodeContent {node} {item} />
-{:else if node instanceof TrackSegment}
-    <FileListNodeLabel {node} {item} {label} />
-{:else if node instanceof Waypoint}
-    <FileListNodeLabel {node} {item} {label} />
+{#if node.type === 'segment' || node.type === 'waypoint'}
+    <FileListNodeLabel {fileState} {node} {label} />
 {:else if recursive}
-    <CollapsibleTreeNode id={item.getId()} bind:this={collapsible}>
+    <CollapsibleTreeNode {id} bind:this={collapsible}>
         {#snippet trigger()}
-            <FileListNodeLabel {node} {item} {label} />
+            <FileListNodeLabel {fileState} {node} {label} />
         {/snippet}
         {#snippet content()}
             <div class="ml-4">
-                {#key node}
-                    <FileListNodeContent {node} {item} />
-                {/key}
+                <FileListNodeContent {fileState} {node} />
             </div>
         {/snippet}
     </CollapsibleTreeNode>
 {:else}
-    <FileListNodeLabel {node} {item} {label} />
+    <FileListNodeLabel {fileState} {node} {label} />
 {/if}
diff --git a/website/src/lib/components/file-list/FileListNodeContent.svelte b/website/src/lib/components/file-list/FileListNodeContent.svelte
index fe6926cc3..63cb8972d 100644
--- a/website/src/lib/components/file-list/FileListNodeContent.svelte
+++ b/website/src/lib/components/file-list/FileListNodeContent.svelte
@@ -1,41 +1,39 @@
 <script lang="ts">
-    import { GPXFile, Track, Waypoint, type AnyGPXTreeElement, type GPXTreeElement } from 'gpx';
     import { getContext, onDestroy, onMount } from 'svelte';
-    import { type Readable } from 'svelte/store';
     import FileListNodeStore from './FileListNodeStore.svelte';
     import FileListNode from './FileListNode.svelte';
     import FileListNodeContent from './FileListNodeContent.svelte';
-    import { ListFileItem, ListLevel, ListWaypointsItem, type ListItem } from './file-list';
-    import type { GPXFileWithStatistics } from '$lib/logic/statistics-tree';
+    import { ListLevel } from './file-list';
     import { allowedMoves, dragging, SortableFileList } from './sortable-file-list';
+    import { engine, type FileState } from '$lib/engine';
+    import type { FileTreeNode } from '$lib/selection-helpers';
 
     let {
+        fileState,
         node,
-        item,
         waypointRoot = false,
     }: {
-        node:
-            | Map<string, Readable<GPXFileWithStatistics | undefined>>
-            | GPXTreeElement<AnyGPXTreeElement>
-            | Waypoint[]
-            | Waypoint;
-        item: ListItem;
+        /** State of the file of the node (not needed for the root). */
+        fileState?: FileState;
+        /** The node whose children are listed, `null` for the list of the files. */
+        node: FileTreeNode | null;
+        /** List the node standing for the waypoints of the file, instead of its tracks. */
         waypointRoot?: boolean;
     } = $props();
 
+    const { files, order } = engine;
+
     let container: HTMLElement;
     let sortableLevel: ListLevel =
-        node instanceof Map
+        node === null
             ? ListLevel.FILE
-            : node instanceof GPXFile
+            : node.type === 'file'
               ? waypointRoot
                   ? ListLevel.WAYPOINTS
-                  : item instanceof ListWaypointsItem
-                    ? ListLevel.WAYPOINT
-                    : ListLevel.TRACK
-              : node instanceof Track
-                ? ListLevel.SEGMENT
-                : ListLevel.WAYPOINT;
+                  : ListLevel.TRACK
+              : node.type === 'waypoints'
+                ? ListLevel.WAYPOINT
+                : ListLevel.SEGMENT;
     let orientation = getContext<'vertical' | 'horizontal'>('orientation');
 
     let canDrop = $derived($dragging !== null && allowedMoves[$dragging].includes(sortableLevel));
@@ -43,18 +41,14 @@
     let sortable: SortableFileList;
 
     onMount(() => {
-        sortable = new SortableFileList(
-            container,
-            node,
-            item,
-            waypointRoot,
-            sortableLevel,
-            orientation
-        );
+        sortable = new SortableFileList(container, node, waypointRoot, sortableLevel, orientation);
     });
 
     $effect(() => {
-        if (sortable && node) {
+        // the elements of the list changed
+        $order;
+        fileState;
+        if (sortable) {
             sortable.updateElements();
         }
     });
@@ -70,45 +64,65 @@
         ? 'flex-col'
         : 'flex-row gap-1'} {canDrop ? 'min-h-5' : ''}"
 >
-    {#if node instanceof Map}
-        {#each node as [fileId, file] (fileId)}
-            <div data-id={fileId}>
-                <FileListNodeStore {file} />
-            </div>
-        {/each}
-    {:else if node instanceof GPXFile}
-        {#if item instanceof ListWaypointsItem}
-            {#each node.wpt as wpt, i (wpt)}
-                <div data-id={i} class="ml-1">
-                    <FileListNode node={wpt} item={item.extend(i)} />
-                </div>
-            {/each}
-        {:else if waypointRoot}
-            {#if node.wpt.length > 0}
-                <div data-id="waypoints">
-                    <FileListNode {node} item={item.extend('waypoints')} />
+    {#if node === null}
+        {#each $order as fileId (fileId)}
+            {@const file = $files.get(fileId)}
+            {#if file}
+                <div data-id={fileId}>
+                    <FileListNodeStore {file} />
                 </div>
             {/if}
-        {:else}
-            {#each node.children as child, i (child)}
-                <div data-id={i}>
-                    <FileListNode node={child} item={item.extend(i)} />
+        {/each}
+    {:else if fileState}
+        {#if node.type === 'file'}
+            {#if waypointRoot}
+                {#if fileState.structure.waypoints.length > 0}
+                    <div data-id="waypoints">
+                        <FileListNode
+                            {fileState}
+                            node={{ type: 'waypoints', fileId: node.fileId }}
+                        />
+                    </div>
+                {/if}
+            {:else}
+                {#each fileState.structure.tracks as track (track.id)}
+                    <div data-id={track.id}>
+                        <FileListNode
+                            {fileState}
+                            node={{ type: 'track', fileId: node.fileId, trackId: track.id }}
+                        />
+                    </div>
+                {/each}
+            {/if}
+        {:else if node.type === 'waypoints'}
+            {#each fileState.structure.waypoints as waypoint (waypoint.id)}
+                <div data-id={waypoint.id} class="ml-1">
+                    <FileListNode
+                        {fileState}
+                        node={{ type: 'waypoint', fileId: node.fileId, waypointId: waypoint.id }}
+                    />
+                </div>
+            {/each}
+        {:else if node.type === 'track'}
+            {#each fileState.structure.tracks.find((t) => t.id === node.trackId)?.segments ?? [] as segment (segment.id)}
+                <div data-id={segment.id} class="ml-1">
+                    <FileListNode
+                        {fileState}
+                        node={{
+                            type: 'segment',
+                            fileId: node.fileId,
+                            trackId: node.trackId,
+                            segmentId: segment.id,
+                        }}
+                    />
                 </div>
             {/each}
         {/if}
-    {:else if node instanceof Track}
-        {#each node.children as child, i (child)}
-            <div data-id={i} class="ml-1">
-                <FileListNode node={child} item={item.extend(i)} />
-            </div>
-        {/each}
     {/if}
 </div>
 
-{#if node instanceof GPXFile && item instanceof ListFileItem}
-    {#if !waypointRoot}
-        <FileListNodeContent {node} {item} waypointRoot={true} />
-    {/if}
+{#if fileState && node?.type === 'file' && !waypointRoot}
+    <FileListNodeContent {fileState} {node} waypointRoot={true} />
 {/if}
 
 <style lang="postcss">
diff --git a/website/src/lib/components/file-list/FileListNodeLabel.svelte b/website/src/lib/components/file-list/FileListNodeLabel.svelte
index 77d5aa66a..c07bea4f3 100644
--- a/website/src/lib/components/file-list/FileListNodeLabel.svelte
+++ b/website/src/lib/components/file-list/FileListNodeLabel.svelte
@@ -18,86 +18,95 @@
         Scissors,
         FileStack,
     } from '@lucide/svelte';
-    import {
-        ListFileItem,
-        ListLevel,
-        ListTrackItem,
-        ListWaypointItem,
-        type ListItem,
-    } from './file-list';
+    import { ListLevel } from './file-list';
     import { getContext } from 'svelte';
-    import { GPXTreeElement, Track, type AnyGPXTreeElement, Waypoint, GPXFile } from 'gpx';
     import { i18n } from '$lib/i18n.svelte';
     import MetadataDialog from '$lib/components/file-list/metadata/MetadataDialog.svelte';
     import { editMetadata } from '$lib/components/file-list/metadata/utils.svelte';
     import StyleDialog from '$lib/components/file-list/style/StyleDialog.svelte';
     import { editStyle } from '$lib/components/file-list/style/utils.svelte';
     import { getSymbolKey, symbols } from '$lib/assets/symbols';
-    import { selection, copied, cut } from '$lib/logic/selection';
-    import { fileActions, pasteSelection } from '$lib/logic/file-actions';
-    import { allHidden } from '$lib/logic/hidden';
+    import { engine, type FileState } from '$lib/engine';
+    import { allHidden } from '$lib/all-hidden';
+    import { normalizeColor } from '$lib/file-colors';
+    import { isHidden } from '$lib/file-visibility';
+    import {
+        elementId,
+        isSelected,
+        selectedElementIds,
+        selectionSize,
+        type FileTreeNode,
+    } from '$lib/selection-helpers';
+    // TODO the clipboard, centering on the selection and the waypoint popup still work on the
+    // previous implementation
+    import { copied, selection as oldSelection } from '$lib/logic/selection';
+    import { pasteSelection } from '$lib/logic/file-actions';
     import { boundsManager } from '$lib/logic/bounds';
-    import { gpxColors, gpxLayers } from '$lib/components/map/gpx-layer/gpx-layers';
-    import { fileStateCollection } from '$lib/logic/file-state';
-    import { waypointPopup } from '$lib/components/map/gpx-layer/gpx-layer-popup';
+    // import { gpxLayers } from '$lib/components/map/gpx-layer/gpx-layers';
+    // import { fileStateCollection } from '$lib/logic/file-state';
+    // import { waypointPopup } from '$lib/components/map/gpx-layer/gpx-layer-popup';
     import { allowedPastes } from './sortable-file-list';
 
     let {
+        fileState,
         node,
-        item,
         label,
     }: {
-        node: GPXTreeElement<AnyGPXTreeElement> | Waypoint[] | Waypoint;
-        item: ListItem;
+        fileState: FileState;
+        node: FileTreeNode;
         label: string | undefined;
     } = $props();
 
+    const { selection } = engine;
+
     let orientation = getContext<'vertical' | 'horizontal'>('orientation');
     let embedding = getContext<boolean>('embedding');
 
-    let singleSelection = $derived($selection.size === 1);
+    const levels = {
+        file: ListLevel.FILE,
+        track: ListLevel.TRACK,
+        segment: ListLevel.SEGMENT,
+        waypoints: ListLevel.WAYPOINTS,
+        waypoint: ListLevel.WAYPOINT,
+    };
+    let level = $derived(levels[node.type]);
+
+    let singleSelection = $derived(selectionSize($selection) === 1);
 
     let nodeColors: string[] = $derived.by(() => {
-        let colors: string[] = [];
-        if (node) {
-            if (node instanceof GPXFile) {
-                let defaultColor = $gpxColors.get(item.getFileId());
-                let style = node.getStyle(defaultColor);
-                colors = style.color;
-            } else if (node instanceof Track) {
-                let style = node.getStyle();
-                if (
-                    style &&
-                    style['gpx_style:color'] &&
-                    !colors.includes(style['gpx_style:color'])
-                ) {
-                    colors.push(style['gpx_style:color']);
-                }
-                if (colors.length === 0) {
-                    let defaultColor = $gpxColors.get(item.getFileId());
-                    if (defaultColor) {
-                        colors.push(defaultColor);
-                    }
-                }
-            }
+        const { tracks } = fileState.structure;
+        if (node.type === 'file') {
+            // the colors defined by the tracks, or else the one of the file
+            const colors = [
+                ...new Set(
+                    tracks.flatMap((track) =>
+                        track.color !== undefined ? [normalizeColor(track.color)] : []
+                    )
+                ),
+            ];
+            return colors.length > 0 ? colors : [fileState.color];
+        } else if (node.type === 'track') {
+            const color = tracks.find((track) => track.id === node.trackId)?.color;
+            return [color !== undefined ? normalizeColor(color) : fileState.color];
         }
-        return colors;
+        return [];
     });
 
-    let symbolKey = $derived(node instanceof Waypoint ? getSymbolKey(node.sym) : undefined);
-
-    let openEditMetadata: boolean = $derived(
-        editMetadata.current && singleSelection && $selection.has(item)
+    let symbolKey = $derived(
+        node.type === 'waypoint'
+            ? getSymbolKey(fileState.structure.waypoints.find((w) => w.id === node.waypointId)?.sym)
+            : undefined
     );
+
+    let selected = $derived(isSelected($selection, node));
+    let openEditMetadata: boolean = $derived(editMetadata.current && singleSelection && selected);
     let openEditStyle: boolean = $derived(
         editStyle.current &&
-            $selection.has(item) &&
-            $selection.getSelected().findIndex((i) => i.getFullId() === item.getFullId()) === 0
+            selected &&
+            selectedElementIds($selection)[0]?.ids[0] === elementId(node)
     );
 
-    let hidden = $derived(
-        item.level === ListLevel.WAYPOINTS ? node._data.hiddenWpt : node._data.hidden
-    );
+    let hidden = $derived(isHidden(fileState, elementId(node)));
 </script>
 
 <!-- svelte-ignore a11y_click_events_have_key_events -->
@@ -105,8 +114,8 @@
 <ContextMenu.Root
     onOpenChange={(open) => {
         if (open) {
-            if (!$selection.has(item)) {
-                selection.selectItem(item);
+            if (!selected) {
+                engine.selectNode(node);
             }
         }
     }}
@@ -119,11 +128,11 @@
                 ? 'h-7'
                 : 'h-9 px-1.5'} pointer-events-auto"
         >
-            {#if item instanceof ListFileItem || item instanceof ListTrackItem}
-                <MetadataDialog bind:open={openEditMetadata} {node} {item} />
-                <StyleDialog bind:open={openEditStyle} {item} />
+            {#if node.type === 'file' || node.type === 'track'}
+                <MetadataDialog bind:open={openEditMetadata} {fileState} {node} />
+                <StyleDialog bind:open={openEditStyle} {fileState} {node} />
             {/if}
-            {#if item.level === ListLevel.FILE || item.level === ListLevel.TRACK}
+            {#if level === ListLevel.FILE || level === ListLevel.TRACK}
                 <div
                     class="absolute {orientation === 'vertical'
                         ? 'top-0 bottom-0 right-0 w-1'
@@ -141,9 +150,7 @@
             <span
                 class="grow text-left truncate ml-1 flex flex-row items-center {hidden
                     ? 'text-muted-foreground'
-                    : ''} {$cut && $copied?.some((i) => i.getFullId() === item.getFullId())
-                    ? 'text-muted-foreground'
-                    : ''}"
+                    : ''} {/* TODO cut elements: the clipboard works on the previous implementation */ ''}"
                 oncontextmenu={(e) => {
                     if (embedding) {
                         e.preventDefault();
@@ -154,37 +161,35 @@
                         // Add to selection instead of opening context menu
                         e.preventDefault();
                         e.stopPropagation();
-                        $selection.toggle(item);
-                        $selection = $selection;
+                        engine.selectNode(node, 'toggle');
                     }
                 }}
                 onmouseenter={() => {
-                    if (item instanceof ListWaypointItem) {
-                        let layer = gpxLayers.getLayer(item.getFileId());
-                        let file = fileStateCollection.getFile(item.getFileId());
-                        if (layer && file) {
-                            let waypoint = file.wpt[item.getWaypointIndex()];
-                            if (waypoint && !waypoint._data.hidden) {
-                                waypointPopup?.setItem({
-                                    item: waypoint,
-                                    fileId: item.getFileId(),
-                                });
-                            }
-                        }
-                    }
+                    // TODO waypoint popup: it needs the waypoint of the previous implementation
+                    // if (node.type === 'waypoint') {
+                    //     let layer = gpxLayers.getLayer(node.fileId);
+                    //     let file = fileStateCollection.getFile(node.fileId);
+                    //     if (layer && file) {
+                    //         let waypoint = file.wpt[waypointIndex];
+                    //         if (waypoint && !waypoint._data.hidden) {
+                    //             waypointPopup?.setItem({ item: waypoint, fileId: node.fileId });
+                    //         }
+                    //     }
+                    // }
                 }}
                 onmouseleave={() => {
-                    if (item instanceof ListWaypointItem) {
-                        let layer = gpxLayers.getLayer(item.getFileId());
-                        if (layer) {
-                            waypointPopup?.setItem(null);
-                        }
-                    }
+                    // TODO waypoint popup
+                    // if (node.type === 'waypoint') {
+                    //     let layer = gpxLayers.getLayer(node.fileId);
+                    //     if (layer) {
+                    //         waypointPopup?.setItem(null);
+                    //     }
+                    // }
                 }}
             >
-                {#if item.level === ListLevel.SEGMENT}
+                {#if level === ListLevel.SEGMENT}
                     <Waypoints size="16" class="mx-1 shrink-0" />
-                {:else if item.level === ListLevel.WAYPOINT}
+                {:else if level === ListLevel.WAYPOINT}
                     {#if symbolKey && symbols[symbolKey].icon}
                         {@const SymbolIcon = symbols[symbolKey].icon}
                         <SymbolIcon size="16" class="mx-1 shrink-0" />
@@ -211,7 +216,7 @@
         </Button>
     </ContextMenu.Trigger>
     <ContextMenu.Content>
-        {#if item instanceof ListFileItem || item instanceof ListTrackItem}
+        {#if node.type === 'file' || node.type === 'track'}
             <ContextMenu.Item
                 disabled={!singleSelection}
                 onclick={() => (editMetadata.current = true)}
@@ -225,15 +230,7 @@
                 {i18n._('menu.style.button')}
             </ContextMenu.Item>
         {/if}
-        <ContextMenu.Item
-            onclick={() => {
-                if ($allHidden) {
-                    fileActions.setHiddenToSelection(false);
-                } else {
-                    fileActions.setHiddenToSelection(true);
-                }
-            }}
-        >
+        <ContextMenu.Item onclick={() => engine.setSelectionHidden(!$allHidden)}>
             {#if $allHidden}
                 <Eye size="16" />
                 {i18n._('menu.unhide')}
@@ -245,20 +242,16 @@
         </ContextMenu.Item>
         <ContextMenu.Separator />
         {#if orientation === 'vertical'}
-            {#if item instanceof ListFileItem}
-                <ContextMenu.Item
-                    disabled={!singleSelection}
-                    onclick={() => fileActions.addNewTrack(item.getFileId())}
-                >
+            {#if node.type === 'file'}
+                <ContextMenu.Item disabled={!singleSelection} onclick={() => engine.newTrack()}>
                     <Plus size="16" />
                     {i18n._('menu.new_track')}
                 </ContextMenu.Item>
                 <ContextMenu.Separator />
-            {:else if item instanceof ListTrackItem}
+            {:else if node.type === 'track'}
                 <ContextMenu.Item
                     disabled={!singleSelection}
-                    onclick={() =>
-                        fileActions.addNewSegment(item.getFileId(), item.getTrackIndex())}
+                    onclick={() => engine.newTrackSegment()}
                 >
                     <Plus size="16" />
                     {i18n._('menu.new_segment')}
@@ -266,8 +259,8 @@
                 <ContextMenu.Separator />
             {/if}
         {/if}
-        {#if item.level !== ListLevel.WAYPOINTS}
-            <ContextMenu.Item onclick={() => selection.selectAll()}>
+        {#if level !== ListLevel.WAYPOINTS}
+            <ContextMenu.Item onclick={() => engine.selectAllSiblings(node)}>
                 <FileStack size="16" />
                 {i18n._('menu.select_all')}
                 <Shortcut key="A" ctrl={true} />
@@ -279,18 +272,18 @@
             <Shortcut key="⏎" ctrl={true} />
         </ContextMenu.Item>
         <ContextMenu.Separator />
-        <ContextMenu.Item onclick={fileActions.duplicateSelection}>
+        <ContextMenu.Item onclick={() => engine.duplicate()}>
             <Copy size="16" />
             {i18n._('menu.duplicate')}
             <Shortcut key="D" ctrl={true} />
         </ContextMenu.Item>
         {#if orientation === 'vertical'}
-            <ContextMenu.Item onclick={() => selection.copySelection()}>
+            <ContextMenu.Item onclick={() => oldSelection.copySelection()}>
                 <ClipboardCopy size="16" />
                 {i18n._('menu.copy')}
                 <Shortcut key="C" ctrl={true} />
             </ContextMenu.Item>
-            <ContextMenu.Item onclick={() => selection.cutSelection()}>
+            <ContextMenu.Item onclick={() => oldSelection.cutSelection()}>
                 <Scissors size="16" />
                 {i18n._('menu.cut')}
                 <Shortcut key="X" ctrl={true} />
@@ -298,7 +291,7 @@
             <ContextMenu.Item
                 disabled={$copied === undefined ||
                     $copied.length === 0 ||
-                    !allowedPastes[$copied[0].level].includes(item.level)}
+                    !allowedPastes[$copied[0].level].includes(level)}
                 onclick={pasteSelection}
             >
                 <ClipboardPaste size="16" />
@@ -307,7 +300,7 @@
             </ContextMenu.Item>
         {/if}
         <ContextMenu.Separator />
-        <ContextMenu.Item onclick={fileActions.deleteSelection}>
+        <ContextMenu.Item onclick={() => engine.delete()}>
             <Trash2 size="16" />
             {i18n._('menu.delete')}
             <Shortcut key="⌫" ctrl={true} />
diff --git a/website/src/lib/components/file-list/FileListNodeStore.svelte b/website/src/lib/components/file-list/FileListNodeStore.svelte
index f6c9b4469..734a7f527 100644
--- a/website/src/lib/components/file-list/FileListNodeStore.svelte
+++ b/website/src/lib/components/file-list/FileListNodeStore.svelte
@@ -4,24 +4,21 @@
 
     import { getContext } from 'svelte';
     import type { Readable } from 'svelte/store';
-    import { ListFileItem } from './file-list';
-    import type { GPXFileWithStatistics } from '$lib/logic/statistics-tree';
+    import type { FileState } from '$lib/engine';
 
     let {
         file,
     }: {
-        file: Readable<GPXFileWithStatistics | undefined>;
+        file: Readable<FileState>;
     } = $props();
 
     let recursive = getContext<boolean>('recursive');
 </script>
 
-{#if $file}
-    {#if recursive}
-        <CollapsibleTree side="left" defaultState="closed" slotInsideTrigger={false}>
-            <FileListNode node={$file.file} item={new ListFileItem($file.file._data.id)} />
-        </CollapsibleTree>
-    {:else}
-        <FileListNode node={$file.file} item={new ListFileItem($file.file._data.id)} />
-    {/if}
+{#if recursive}
+    <CollapsibleTree side="left" defaultState="closed" slotInsideTrigger={false}>
+        <FileListNode fileState={$file} node={{ type: 'file', fileId: $file.structure.id }} />
+    </CollapsibleTree>
+{:else}
+    <FileListNode fileState={$file} node={{ type: 'file', fileId: $file.structure.id }} />
 {/if}
diff --git a/website/src/lib/components/file-list/metadata/MetadataDialog.svelte b/website/src/lib/components/file-list/metadata/MetadataDialog.svelte
index 2af578ead..b7219471e 100644
--- a/website/src/lib/components/file-list/metadata/MetadataDialog.svelte
+++ b/website/src/lib/components/file-list/metadata/MetadataDialog.svelte
@@ -5,35 +5,31 @@
     import { Label } from '$lib/components/ui/label/index.js';
     import * as Popover from '$lib/components/ui/popover';
     import { Save } from '@lucide/svelte';
-    import { ListFileItem, ListTrackItem, type ListItem } from '../file-list';
-    import { GPXTreeElement, Track, type AnyGPXTreeElement, Waypoint, GPXFile } from 'gpx';
     import { i18n } from '$lib/i18n.svelte';
     import { editMetadata } from '$lib/components/file-list/metadata/utils.svelte';
-    import { fileActionManager } from '$lib/logic/file-action-manager';
+    import { engine, type FileState } from '$lib/engine';
+    import type { FileTreeNode } from '$lib/selection-helpers';
 
     let {
+        fileState,
         node,
-        item,
         open = $bindable(),
     }: {
-        node: GPXTreeElement<AnyGPXTreeElement> | Waypoint[] | Waypoint;
-        item: ListItem;
+        fileState: FileState;
+        node: FileTreeNode;
         open: boolean;
     } = $props();
 
+    let track = $derived(
+        node.type === 'track'
+            ? fileState.structure.tracks.find((track) => track.id === node.trackId)
+            : undefined
+    );
     let name: string = $derived(
-        node instanceof GPXFile
-            ? (node.metadata.name ?? '')
-            : node instanceof Track
-              ? (node.name ?? '')
-              : ''
+        node.type === 'file' ? fileState.structure.name : (track?.name ?? '')
     );
     let description: string = $derived(
-        node instanceof GPXFile
-            ? (node.metadata.desc ?? '')
-            : node instanceof Track
-              ? (node.desc ?? '')
-              : ''
+        node.type === 'file' ? (fileState.structure.desc ?? '') : (track?.desc ?? '')
     );
 
     $effect(() => {
@@ -53,18 +49,8 @@
         <Button
             variant="outline"
             onclick={() => {
-                fileActionManager.applyToFile(item.getFileId(), (file) => {
-                    if (item instanceof ListFileItem && node instanceof GPXFile) {
-                        file.metadata.name = name;
-                        file.metadata.desc = description;
-                        if (file.trk.length === 1) {
-                            file.trk[0].name = name;
-                        }
-                    } else if (item instanceof ListTrackItem && node instanceof Track) {
-                        file.trk[item.getTrackIndex()].name = name;
-                        file.trk[item.getTrackIndex()].desc = description;
-                    }
-                });
+                // the metadata of the selected elements are changed
+                engine.metadata(name, description);
                 open = false;
             }}
         >
diff --git a/website/src/lib/components/file-list/sortable-file-list.ts b/website/src/lib/components/file-list/sortable-file-list.ts
index a0902dc19..221279bc4 100644
--- a/website/src/lib/components/file-list/sortable-file-list.ts
+++ b/website/src/lib/components/file-list/sortable-file-list.ts
@@ -1,15 +1,15 @@
 import { isMac } from '$lib/utils';
 import Sortable, { type Direction } from 'sortablejs/Sortable';
-import { ListItem, ListLevel, ListRootItem } from './file-list';
-import { selection } from '$lib/logic/selection';
-import { getFileIds, moveItems } from '$lib/logic/file-actions';
-import { get, writable, type Readable } from 'svelte/store';
-import { settings } from '$lib/logic/settings';
-import type { GPXFileWithStatistics } from '$lib/logic/statistics-tree';
-import type { AnyGPXTreeElement, GPXTreeElement, Waypoint } from 'gpx';
+import { ListLevel } from './file-list';
+import { get, writable } from 'svelte/store';
 import { tick } from 'svelte';
-
-const { fileOrder } = settings;
+import { engine } from '$lib/engine';
+import { isSelected, type FileTreeNode } from '$lib/selection-helpers';
+// TODO moving elements between parents is not available in the engine yet
+// import { ListItem, ListRootItem } from './file-list';
+// import { getFileIds, moveItems } from '$lib/logic/file-actions';
+// import { settings } from '$lib/logic/settings';
+// const { fileOrder } = settings;
 
 export const allowedMoves: Record<ListLevel, ListLevel[]> = {
     [ListLevel.ROOT]: [],
@@ -31,13 +31,12 @@ export const allowedPastes: Record<ListLevel, ListLevel[]> = {
 
 export const dragging = writable<ListLevel | null>(null);
 
+/**
+ * Makes a list of the file tree sortable and selectable. The elements of the list are the
+ * children of `parent` (the files when `parent` is null), their ids are in their `data-id`.
+ */
 export class SortableFileList {
-    private _node:
-        | Map<string, Readable<GPXFileWithStatistics | undefined>>
-        | GPXTreeElement<AnyGPXTreeElement>
-        | Waypoint[]
-        | Waypoint;
-    private _item: ListItem;
+    private _parent: FileTreeNode | null;
     private _sortableLevel: ListLevel;
     private _container: HTMLElement;
     private _sortable: Sortable | null = null;
@@ -47,26 +46,24 @@ export class SortableFileList {
 
     constructor(
         container: HTMLElement,
-        node:
-            | Map<string, Readable<GPXFileWithStatistics | undefined>>
-            | GPXTreeElement<AnyGPXTreeElement>
-            | Waypoint[]
-            | Waypoint,
-        item: ListItem,
+        parent: FileTreeNode | null,
         waypointRoot: boolean,
         sortableLevel: ListLevel,
         orientation: Direction
     ) {
-        this._node = node;
-        this._item = item;
+        this._parent = parent;
         this._sortableLevel = sortableLevel;
         this._container = container;
+        // TODO only the order of the files can be changed for now: the other lists neither sort
+        // nor exchange elements (allowedMoves, to be used again once the engine can move elements)
+        const sortable = sortableLevel === ListLevel.FILE;
         this._sortable = Sortable.create(container, {
             group: {
                 name: sortableLevel,
-                pull: allowedMoves[sortableLevel],
-                put: true,
+                pull: sortable ? allowedMoves[sortableLevel] : false,
+                put: sortable ? [ListLevel.FILE] : false,
             },
+            sort: sortable,
             direction: orientation,
             forceAutoScrollFallback: true,
             multiDrag: true,
@@ -80,76 +77,103 @@ export class SortableFileList {
             onEnd: () => dragging.set(null),
             onSort: (e: Sortable.SortableEvent) => this.onSort(e),
         });
-        Object.defineProperty(this._sortable, '_item', {
-            value: item,
-            writable: true,
-        });
-
         Object.defineProperty(this._sortable, '_waypointRoot', {
             value: waypointRoot,
             writable: true,
         });
 
         this._unsubscribes.push(
-            selection.subscribe(() => tick().then(() => this.updateFromSelection()))
+            engine.selection.subscribe(() => tick().then(() => this.updateFromSelection()))
         );
-        this._unsubscribes.push(fileOrder.subscribe(() => this.updateFromFileOrder()));
+        this._unsubscribes.push(engine.order.subscribe(() => this.updateFromFileOrder()));
+    }
+
+    /** The node of a child of the list. */
+    childNode(id: string): FileTreeNode | undefined {
+        const parent = this._parent;
+        switch (this._sortableLevel) {
+            case ListLevel.FILE:
+                return { type: 'file', fileId: id };
+            case ListLevel.TRACK:
+                return parent ? { type: 'track', fileId: parent.fileId, trackId: id } : undefined;
+            case ListLevel.SEGMENT:
+                return parent?.type === 'track'
+                    ? {
+                          type: 'segment',
+                          fileId: parent.fileId,
+                          trackId: parent.trackId,
+                          segmentId: id,
+                      }
+                    : undefined;
+            case ListLevel.WAYPOINTS:
+                return parent ? { type: 'waypoints', fileId: parent.fileId } : undefined;
+            case ListLevel.WAYPOINT:
+                return parent
+                    ? { type: 'waypoint', fileId: parent.fileId, waypointId: id }
+                    : undefined;
+        }
     }
 
     onSort(e: Sortable.SortableEvent) {
         this.updateToFileOrder();
 
-        const from = Sortable.get(e.from);
-        const to = Sortable.get(e.to);
+        // TODO moving elements between parents: the engine has no command for it yet, the code
+        // below worked on the previous implementation
+        // onSort(e: Sortable.SortableEvent) {
+        //     this.updateToFileOrder();
 
-        if (!from || !to) {
-            return;
-        }
+        //     const from = Sortable.get(e.from);
+        //     const to = Sortable.get(e.to);
 
-        let fromItem = from._item;
-        let toItem = to._item;
+        //     if (!from || !to) {
+        //         return;
+        //     }
 
-        if (this._item === toItem && !(fromItem instanceof ListRootItem)) {
-            // Event is triggered on source and destination list, only handle it once
-            let fromItems = [];
-            let toItems = [];
+        //     let fromItem = from._item;
+        //     let toItem = to._item;
 
-            if (from._waypointRoot) {
-                fromItems = [fromItem.extend('waypoints')];
-            } else {
-                let oldIndices: number[] =
-                    e.oldIndicies.length > 0 ? e.oldIndicies.map((i) => i.index) : [e.oldIndex];
-                oldIndices = oldIndices.filter((i) => i >= 0);
-                oldIndices.sort((a, b) => a - b);
+        //     if (this._item === toItem && !(fromItem instanceof ListRootItem)) {
+        //         // Event is triggered on source and destination list, only handle it once
+        //         let fromItems = [];
+        //         let toItems = [];
 
-                fromItems = oldIndices.map((i) => fromItem.extend(i));
-            }
+        //         if (from._waypointRoot) {
+        //             fromItems = [fromItem.extend('waypoints')];
+        //         } else {
+        //             let oldIndices: number[] =
+        //                 e.oldIndicies.length > 0 ? e.oldIndicies.map((i) => i.index) : [e.oldIndex];
+        //             oldIndices = oldIndices.filter((i) => i >= 0);
+        //             oldIndices.sort((a, b) => a - b);
 
-            if (from._waypointRoot && to._waypointRoot) {
-                toItems = [toItem.extend('waypoints')];
-            } else {
-                if (to._waypointRoot) {
-                    toItem = toItem.extend('waypoints');
-                }
+        //             fromItems = oldIndices.map((i) => fromItem.extend(i));
+        //         }
 
-                let newIndices: number[] =
-                    e.newIndicies.length > 0 ? e.newIndicies.map((i) => i.index) : [e.newIndex];
-                newIndices = newIndices.filter((i) => i >= 0);
-                newIndices.sort((a, b) => a - b);
+        //         if (from._waypointRoot && to._waypointRoot) {
+        //             toItems = [toItem.extend('waypoints')];
+        //         } else {
+        //             if (to._waypointRoot) {
+        //                 toItem = toItem.extend('waypoints');
+        //             }
 
-                if (toItem instanceof ListRootItem) {
-                    let newFileIds = getFileIds(newIndices.length);
-                    toItems = newIndices.map((i, index) => {
-                        get(fileOrder).splice(i, 0, newFileIds[index]);
-                        return this._item.extend(newFileIds[index]);
-                    });
-                } else {
-                    toItems = newIndices.map((i) => toItem.extend(i));
-                }
-            }
+        //             let newIndices: number[] =
+        //                 e.newIndicies.length > 0 ? e.newIndicies.map((i) => i.index) : [e.newIndex];
+        //             newIndices = newIndices.filter((i) => i >= 0);
+        //             newIndices.sort((a, b) => a - b);
 
-            moveItems(fromItem, toItem, fromItems, toItems);
-        }
+        //             if (toItem instanceof ListRootItem) {
+        //                 let newFileIds = getFileIds(newIndices.length);
+        //                 toItems = newIndices.map((i, index) => {
+        //                     get(fileOrder).splice(i, 0, newFileIds[index]);
+        //                     return this._item.extend(newFileIds[index]);
+        //                 });
+        //             } else {
+        //                 toItems = newIndices.map((i) => toItem.extend(i));
+        //             }
+        //         }
+
+        //         moveItems(fromItem, toItem, fromItems, toItems);
+        //     }
+        // }
     }
 
     updateFromSelection() {
@@ -157,11 +181,12 @@ export class SortableFileList {
         if (changed.length === 0) {
             return;
         }
-        const selection_ = get(selection);
+        const selection_ = get(engine.selection);
         for (let id of changed) {
             let element = this._elements[id];
-            if (element) {
-                if (selection_.has(this._item.extend(id))) {
+            let node = this.childNode(id);
+            if (element && node) {
+                if (isSelected(selection_, node)) {
                     Sortable.utils.select(element);
                     element.scrollIntoView({
                         behavior: 'smooth',
@@ -183,27 +208,42 @@ export class SortableFileList {
             this._updatingSelection = false;
             return;
         }
-        selection.update(($selection) => {
-            $selection.clear();
-            Object.entries(this._elements).forEach(([id, element]) => {
-                $selection.set(
-                    this._item.extend(this.getRealId(id)),
-                    element.classList.contains('sortable-selected')
-                );
-            });
 
-            if (
-                e.originalEvent &&
-                !(e.originalEvent.ctrlKey || e.originalEvent.metaKey || e.originalEvent.shiftKey) &&
-                ($selection.size > 1 ||
-                    !$selection.has(this._item.extend(this.getRealId(changed[0]))))
-            ) {
-                // Fix bug that sometimes causes a single select to be treated as a multi-select
-                $selection.clear();
-                $selection.set(this._item.extend(this.getRealId(changed[0])), true);
+        let selected = Object.entries(this._elements)
+            .filter(([, element]) => element.classList.contains('sortable-selected'))
+            .map(([id]) => id);
+
+        if (
+            e.originalEvent &&
+            !(e.originalEvent.ctrlKey || e.originalEvent.metaKey || e.originalEvent.shiftKey) &&
+            (selected.length > 1 || !selected.includes(changed[0]))
+        ) {
+            // Fix bug that sometimes causes a single select to be treated as a multi-select
+            selected = [changed[0]];
+        }
+
+        const parent = this._parent;
+        if (selected.length === 0 || !this.childNode(selected[0])) {
+            engine.select([]);
+        } else {
+            switch (this._sortableLevel) {
+                case ListLevel.FILE:
+                    engine.select(selected);
+                    break;
+                case ListLevel.TRACK:
+                    engine.selectTracks(parent!.fileId, selected);
+                    break;
+                case ListLevel.SEGMENT:
+                    engine.selectSegments(parent!.fileId, (parent as any).trackId, selected);
+                    break;
+                case ListLevel.WAYPOINTS:
+                    engine.selectWaypointGroup(parent!.fileId);
+                    break;
+                case ListLevel.WAYPOINT:
+                    engine.selectWaypoints(parent!.fileId, selected);
+                    break;
             }
-            return $selection;
-        });
+        }
         this._updatingSelection = false;
     }
 
@@ -212,7 +252,7 @@ export class SortableFileList {
             return;
         }
 
-        const fileOrder_ = get(fileOrder);
+        const fileOrder_ = get(engine.order);
         const sortableOrder = this._sortable.toArray();
 
         if (
@@ -228,24 +268,25 @@ export class SortableFileList {
             return;
         }
 
-        const fileOrder_ = get(fileOrder);
+        const fileOrder_ = get(engine.order);
         const sortableOrder = this._sortable.toArray();
 
         if (
             fileOrder_.length !== sortableOrder.length ||
             fileOrder_.some((value, index) => value !== sortableOrder[index])
         ) {
-            fileOrder.set(sortableOrder);
+            engine.reorder(sortableOrder, 0);
         }
     }
 
     updateElements() {
         this._elements = {};
+        const files = get(engine.files);
         this._container.childNodes.forEach((element) => {
             if (element instanceof HTMLElement) {
                 let attr = element.getAttribute('data-id');
                 if (attr) {
-                    if (this._node instanceof Map && !this._node.has(attr)) {
+                    if (this._sortableLevel === ListLevel.FILE && !files.has(attr)) {
                         element.remove();
                     } else {
                         this._elements[attr] = element;
@@ -262,23 +303,16 @@ export class SortableFileList {
     }
 
     getChangedIds() {
-        let changed: (string | number)[] = [];
-        const selection_ = get(selection);
+        let changed: string[] = [];
+        const selection_ = get(engine.selection);
         Object.entries(this._elements).forEach(([id, element]) => {
-            let realId = this.getRealId(id);
-            let realItem = this._item.extend(realId);
-            let inSelection = selection_.has(realItem);
-            let isSelected = element.classList.contains('sortable-selected');
-            if (inSelection !== isSelected) {
-                changed.push(realId);
+            const node = this.childNode(id);
+            let inSelection = node !== undefined && isSelected(selection_, node);
+            let isSelectedInList = element.classList.contains('sortable-selected');
+            if (inSelection !== isSelectedInList) {
+                changed.push(id);
             }
         });
         return changed;
     }
-
-    getRealId(id: string | number) {
-        return this._sortableLevel === ListLevel.FILE || this._sortableLevel === ListLevel.WAYPOINTS
-            ? id
-            : parseInt(id as string);
-    }
 }
diff --git a/website/src/lib/components/file-list/style/StyleDialog.svelte b/website/src/lib/components/file-list/style/StyleDialog.svelte
index b4bed0272..262b0ed34 100644
--- a/website/src/lib/components/file-list/style/StyleDialog.svelte
+++ b/website/src/lib/components/file-list/style/StyleDialog.svelte
@@ -5,30 +5,26 @@
     import { Slider } from '$lib/components/ui/slider';
     import * as Popover from '$lib/components/ui/popover';
     import { Save } from '@lucide/svelte';
-    import {
-        ListFileItem,
-        ListTrackItem,
-        type ListItem,
-    } from '$lib/components/file-list/file-list';
     import { editStyle } from '$lib/components/file-list/style/utils.svelte';
     import { i18n } from '$lib/i18n.svelte';
-    import type { LineStyleExtension } from 'gpx';
     import { settings } from '$lib/logic/settings';
-    import { selection } from '$lib/logic/selection';
-    import { fileStateCollection } from '$lib/logic/file-state';
-    import { gpxLayers } from '$lib/components/map/gpx-layer/gpx-layers';
+    import { engine, type FileState } from '$lib/engine';
+    import { normalizeColor } from '$lib/file-colors';
+    import { selectedFileIds, type FileTreeNode } from '$lib/selection-helpers';
     import { untrack } from 'svelte';
-    import { fileActions } from '$lib/logic/file-actions';
 
     let {
-        item,
+        fileState,
+        node,
         open = $bindable(),
     }: {
-        item: ListItem;
+        fileState: FileState;
+        node: FileTreeNode;
         open: boolean;
     } = $props();
 
     const { defaultOpacity, defaultWidth } = settings;
+    const { files, selection } = engine;
 
     let color: string = $state('');
     let opacity: number = $state(0);
@@ -37,45 +33,24 @@
     let opacityChanged = $state(false);
     let widthChanged = $state(false);
 
+    // TODO the inputs used to come from the last selected item, they now come from this node
     function setStyleInputs() {
         opacity = $defaultOpacity;
         width = $defaultWidth;
+        color = fileState.color;
 
-        $selection.forEach((item) => {
-            if (item instanceof ListFileItem) {
-                let file = fileStateCollection.getFile(item.getFileId());
-                let layer = gpxLayers.getLayer(item.getFileId());
-                if (file && layer) {
-                    let style = file.getStyle();
-                    color = layer.layerColor;
-                    if (style.opacity.length > 0) {
-                        opacity = style.opacity[0];
-                    }
-                    if (style.width.length > 0) {
-                        width = style.width[0];
-                    }
-                }
-            } else if (item instanceof ListTrackItem) {
-                let file = fileStateCollection.getFile(item.getFileId());
-                let layer = gpxLayers.getLayer(item.getFileId());
-                if (file && layer) {
-                    color = layer.layerColor;
-                    let track = file.trk[item.getTrackIndex()];
-                    let style = track.getStyle();
-                    if (style) {
-                        if (style['gpx_style:color']) {
-                            color = style['gpx_style:color'];
-                        }
-                        if (style['gpx_style:opacity']) {
-                            opacity = style['gpx_style:opacity'];
-                        }
-                        if (style['gpx_style:width']) {
-                            width = style['gpx_style:width'];
-                        }
-                    }
-                }
+        const { tracks } = fileState.structure;
+        if (node.type === 'file') {
+            opacity = tracks.find((track) => track.opacity !== undefined)?.opacity ?? opacity;
+            width = tracks.find((track) => track.width !== undefined)?.width ?? width;
+        } else if (node.type === 'track') {
+            const track = tracks.find((track) => track.id === node.trackId);
+            if (track) {
+                color = track.color !== undefined ? normalizeColor(track.color) : color;
+                opacity = track.opacity ?? opacity;
+                width = track.width ?? width;
             }
-        });
+        }
 
         colorChanged = false;
         opacityChanged = false;
@@ -95,24 +70,18 @@
     });
 
     function applyStyle() {
-        let style: LineStyleExtension = {};
-        if (colorChanged) {
-            style['gpx_style:color'] = color;
-        }
-        if (opacityChanged) {
-            style['gpx_style:opacity'] = opacity;
-        }
-        if (widthChanged) {
-            style['gpx_style:width'] = width;
-        }
-        fileActions.setStyleToSelection(style);
+        engine.style({
+            color: colorChanged ? color : undefined,
+            opacity: opacityChanged ? opacity : undefined,
+            width: widthChanged ? width : undefined,
+        });
 
-        if (item instanceof ListFileItem && $selection.size === fileStateCollection.size) {
-            if (style['gpx_style:opacity']) {
-                $defaultOpacity = style['gpx_style:opacity'];
+        if (node.type === 'file' && selectedFileIds($selection).length === $files.size) {
+            if (opacityChanged) {
+                $defaultOpacity = opacity;
             }
-            if (style['gpx_style:width']) {
-                $defaultWidth = style['gpx_style:width'];
+            if (widthChanged) {
+                $defaultWidth = width;
             }
         }
 
diff --git a/website/src/lib/engine.ts b/website/src/lib/engine.ts
index b5bfe54ce..c1dd5b0d5 100644
--- a/website/src/lib/engine.ts
+++ b/website/src/lib/engine.ts
@@ -2,6 +2,7 @@ import { browser } from '$app/environment';
 import { get, writable, type Readable, type Writable } from 'svelte/store';
 import { FileColorAllocator, normalizeColor } from '$lib/file-colors';
 import { setHidden, type Visibility } from '$lib/file-visibility';
+import { selectedElementIds, type FileTreeNode } from '$lib/selection-helpers';
 import type { Feature, FeatureCollection, LineString, Point } from 'geojson';
 import type { FileStatistics, FileStructure, Selection } from 'gpx-rs';
 
@@ -215,6 +216,78 @@ class Engine {
         return this.run((w) => w.reorder(idsToBytes(fileIds), index));
     }
 
+    /** Selects a node of the file tree. */
+    selectNode(node: FileTreeNode, mode: SelectMode = 'replace') {
+        switch (node.type) {
+            case 'file':
+                return this.select([node.fileId], mode);
+            case 'track':
+                return this.selectTracks(node.fileId, [node.trackId], mode);
+            case 'segment':
+                return this.selectSegments(node.fileId, node.trackId, [node.segmentId], mode);
+            case 'waypoints':
+                return this.selectWaypointGroup(node.fileId, mode);
+            case 'waypoint':
+                return this.selectWaypoints(node.fileId, [node.waypointId], mode);
+        }
+    }
+
+    /** Selects the node and its siblings (all the files, the tracks of a file, and so on). */
+    selectAllSiblings(node: FileTreeNode) {
+        const state = get(this._files).get(node.fileId);
+        if (node.type === 'file' || !state) {
+            return this.selectAll();
+        }
+        const { tracks, waypoints } = get(state).structure;
+        switch (node.type) {
+            case 'track':
+                return this.selectTracks(
+                    node.fileId,
+                    tracks.map((track) => track.id)
+                );
+            case 'segment':
+                return this.selectSegments(
+                    node.fileId,
+                    node.trackId,
+                    tracks.find((track) => track.id === node.trackId)?.segments.map((s) => s.id) ??
+                        []
+                );
+            case 'waypoint':
+                return this.selectWaypoints(
+                    node.fileId,
+                    waypoints.map((waypoint) => waypoint.id)
+                );
+            case 'waypoints':
+                return this.selectWaypointGroup(node.fileId);
+        }
+    }
+
+    // Edits of the selection
+
+    newTrack() {
+        return this.run((w) => w.new_track());
+    }
+
+    newTrackSegment() {
+        return this.run((w) => w.new_track_segment());
+    }
+
+    metadata(name: string, desc: string) {
+        return this.run((w) => w.metadata(name, desc));
+    }
+
+    /** Only the given fields are changed. */
+    style(style: { color?: string; opacity?: number; width?: number }) {
+        return this.run((w) => w.style(style.color, style.opacity, style.width));
+    }
+
+    /** Hides or shows the selected elements. */
+    setSelectionHidden(hidden: boolean) {
+        selectedElementIds(get(this._selection)).forEach(({ fileId, ids }) =>
+            this.setHidden(fileId, ids, hidden)
+        );
+    }
+
     /**
      * Hides or shows elements of a file (see `FileState.visibility`). What was set explicitly
      * below these elements is reset, so that hiding a file then showing one of its segments
diff --git a/website/src/lib/selection-helpers.test.ts b/website/src/lib/selection-helpers.test.ts
index bc17f553e..ee29ada01 100644
--- a/website/src/lib/selection-helpers.test.ts
+++ b/website/src/lib/selection-helpers.test.ts
@@ -1,12 +1,17 @@
 import { describe, it } from 'node:test';
 import assert from 'node:assert/strict';
-import type { Selection } from 'gpx-rs';
+import type { FileStructure, Selection } from 'gpx-rs';
+import type { VisibilityState } from './file-visibility';
 import {
+    elementId,
     hasSelectionWithin,
     isCovered,
     isEmpty,
     isSelected,
+    isSelectionHidden,
+    selectedElementIds,
     selectedFileIds,
+    selectionSize,
     type FileTreeNode,
 } from './selection-helpers';
 
@@ -63,6 +68,36 @@ describe('selection helpers', () => {
         assert.deepEqual(selectedFileIds(waypoint('W1')), ['F1']);
     });
 
+    it('gives the id of the element of a node', () => {
+        assert.deepEqual(
+            Object.keys(nodes).map((name) => elementId(nodes[name])),
+            ['F1', 'F2', 'T1', 'T2', 'S1', 'S2', 'S3', 'F1:waypoints', 'W1', 'W2', 'F2:waypoints']
+        );
+    });
+
+    it('counts the selected elements', () => {
+        assert.equal(selectionSize(empty), 0);
+        assert.equal(selectionSize(files('F1', 'F2')), 2);
+        assert.equal(selectionSize(tracks('T1')), 1);
+        assert.equal(selectionSize(segments('T1', 'S1', 'S2')), 2);
+        assert.equal(selectionSize(waypoints), 1);
+        assert.equal(selectionSize(waypoint('W1', 'W2')), 2);
+    });
+
+    it('lists the ids of the selected elements by file', () => {
+        assert.deepEqual(selectedElementIds(empty), []);
+        assert.deepEqual(selectedElementIds(files('F1', 'F2')), [
+            { fileId: 'F1', ids: ['F1'] },
+            { fileId: 'F2', ids: ['F2'] },
+        ]);
+        assert.deepEqual(selectedElementIds(tracks('T1', 'T2')), [
+            { fileId: 'F1', ids: ['T1', 'T2'] },
+        ]);
+        assert.deepEqual(selectedElementIds(segments('T1', 'S1')), [{ fileId: 'F1', ids: ['S1'] }]);
+        assert.deepEqual(selectedElementIds(waypoints), [{ fileId: 'F1', ids: ['F1:waypoints'] }]);
+        assert.deepEqual(selectedElementIds(waypoint('W1')), [{ fileId: 'F1', ids: ['W1'] }]);
+    });
+
     describe('isSelected', () => {
         it('matches the selected nodes only', () => {
             assert.deepEqual(matching(empty, isSelected), []);
@@ -137,4 +172,48 @@ describe('selection helpers', () => {
             assert.deepEqual(matching(files('F1'), hasSelectionWithin), ['F1']);
         });
     });
+
+    describe('isSelectionHidden', () => {
+        const segment = (id: string) => ({ id, rev: id, length: 2 });
+        const structure: FileStructure = {
+            id: 'F1',
+            name: 'file',
+            waypointsRev: 'rev',
+            waypoints: [{ id: 'W1' }, { id: 'W2' }],
+            tracks: [
+                { id: 'T1', segments: [segment('S1'), segment('S2')] },
+                { id: 'T2', segments: [segment('S3')] },
+            ],
+        };
+        const states = (...hidden: string[]) =>
+            new Map<string, VisibilityState>([
+                [
+                    'F1',
+                    { structure, visibility: new Map(hidden.map((id) => [id, false] as const)) },
+                ],
+            ]);
+
+        it('is false when nothing is selected', () => {
+            assert.equal(isSelectionHidden(empty, states('F1')), false);
+        });
+
+        it('is true when everything selected is hidden', () => {
+            assert.equal(isSelectionHidden(files('F1'), states('F1')), true);
+            assert.equal(isSelectionHidden(tracks('T1', 'T2'), states('T1', 'T2')), true);
+            // through a hidden parent
+            assert.equal(isSelectionHidden(segments('T1', 'S1', 'S2'), states('T1')), true);
+            assert.equal(isSelectionHidden(waypoint('W1', 'W2'), states('F1:waypoints')), true);
+            assert.equal(isSelectionHidden(waypoints, states('F1:waypoints')), true);
+        });
+
+        it('is false as soon as one selected element is visible', () => {
+            assert.equal(isSelectionHidden(files('F1'), states()), false);
+            assert.equal(isSelectionHidden(tracks('T1', 'T2'), states('T1')), false);
+            assert.equal(isSelectionHidden(waypoint('W1', 'W2'), states('W1')), false);
+        });
+
+        it('is false for files that are not known', () => {
+            assert.equal(isSelectionHidden(files('F1', 'F2'), states('F1')), false);
+        });
+    });
 });
diff --git a/website/src/lib/selection-helpers.ts b/website/src/lib/selection-helpers.ts
index ba4c11b3d..d50d88b2b 100644
--- a/website/src/lib/selection-helpers.ts
+++ b/website/src/lib/selection-helpers.ts
@@ -1,4 +1,5 @@
 import type { Selection } from 'gpx-rs';
+import { isHidden, waypointsKey, type VisibilityState } from '$lib/file-visibility';
 
 /**
  * An element of the file tree, to ask questions about the selection:
@@ -15,6 +16,25 @@ export type FileTreeNode =
     | { type: 'waypoints'; fileId: string }
     | { type: 'waypoint'; fileId: string; waypointId: string };
 
+/**
+ * The id of the element of a node, as used by the visibility (`waypointsKey` for the waypoints
+ * node).
+ */
+export function elementId(node: FileTreeNode): string {
+    switch (node.type) {
+        case 'file':
+            return node.fileId;
+        case 'track':
+            return node.trackId;
+        case 'segment':
+            return node.segmentId;
+        case 'waypoints':
+            return waypointsKey(node.fileId);
+        case 'waypoint':
+            return node.waypointId;
+    }
+}
+
 export function isEmpty(selection: Selection): boolean {
     return selection.type === 'empty';
 }
@@ -31,6 +51,45 @@ export function selectedFileIds(selection: Selection): string[] {
     }
 }
 
+/** Number of selected elements (the waypoints node counts for one). */
+export function selectionSize(selection: Selection): number {
+    switch (selection.type) {
+        case 'empty':
+            return 0;
+        case 'file':
+            return selection.fileIds.length;
+        case 'track':
+            return selection.trackIds.length;
+        case 'segment':
+            return selection.segmentIds.length;
+        case 'waypoints':
+            return 1;
+        case 'waypoint':
+            return selection.waypointIds.length;
+    }
+}
+
+/**
+ * The ids of the selected elements, by file, as used by the visibility (a file, its tracks, its
+ * segments, its waypoints, or `waypointsKey` for the waypoints node).
+ */
+export function selectedElementIds(selection: Selection): { fileId: string; ids: string[] }[] {
+    switch (selection.type) {
+        case 'empty':
+            return [];
+        case 'file':
+            return selection.fileIds.map((fileId) => ({ fileId, ids: [fileId] }));
+        case 'track':
+            return [{ fileId: selection.fileId, ids: selection.trackIds }];
+        case 'segment':
+            return [{ fileId: selection.fileId, ids: selection.segmentIds }];
+        case 'waypoints':
+            return [{ fileId: selection.fileId, ids: [waypointsKey(selection.fileId)] }];
+        case 'waypoint':
+            return [{ fileId: selection.fileId, ids: selection.waypointIds }];
+    }
+}
+
 /** Whether the node itself is selected. */
 export function isSelected(selection: Selection, node: FileTreeNode): boolean {
     switch (node.type) {
@@ -107,3 +166,21 @@ export function hasSelectionWithin(selection: Selection, node: FileTreeNode): bo
             return isSelected(selection, node);
     }
 }
+
+/**
+ * Whether all the selected elements are hidden (false when nothing is selected). `states` holds
+ * the files by id: an element of an unknown file is not hidden.
+ */
+export function isSelectionHidden(
+    selection: Selection,
+    states: ReadonlyMap<string, VisibilityState>
+): boolean {
+    const selected = selectedElementIds(selection);
+    return (
+        selected.length > 0 &&
+        selected.every(({ fileId, ids }) => {
+            const state = states.get(fileId);
+            return state !== undefined && ids.every((id) => isHidden(state, id));
+        })
+    );
+}