[Mobile] Enable multi-node selection in Scene Tree

[FarizzDev]

[Mobile] Enable multi-node selection in Scene Tree (e.g., double-tap and drag or gesture-based selection)

Summary

Allow users to select multiple nodes in the Scene panel tree view on Godot Mobile, using intuitive gestures such as double-tap and drag or long-press and drag.

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Motivation

On desktop, selecting multiple nodes in the Scene tab (tree view) is straightforward using Ctrl+Click or Shift+Click.
On mobile, there's no equivalent, forcing users to select nodes one by one — which is inefficient, especially for scenes with many children.

Mobile developers using Godot on Android or iOS could greatly benefit from a way to multi-select nodes, bringing the mobile workflow closer to the desktop experience.

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Use Cases

• Quickly selecting multiple nodes to group or reparent them
• Mass deleting nodes in the Scene tree
• Editing multiple properties (e.g., visibility, transform) at once
• Organizing scene hierarchy efficiently on a touchscreen device
• Dragging multiple nodes to reorder within the tree
• Dropping selected nodes into another node to reparent them as children

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Proposal

Introduce a touch gesture for multi-selecting nodes in the Scene tree panel on mobile.

Suggested UX ideas:

• Double-tap and drag vertically to select all nodes touched in the swipe range
• Or, long-press a node, then drag to extend selection
• Another alternative: enter a “selection mode” with a toggle icon, allowing tap-to-select-multiple behavior (like checkboxes)

Once selected, nodes should:

• Be visually highlighted, just like desktop
• Be draggable as a group, allowing:
  • Reordering nodes
  • Dragging them into a parent node to change hierarchy
• Support all relevant actions (delete, duplicate, group, etc.)

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Alternatives

• Add a toggle button to activate "Multi-select mode" in the Scene panel
• Swipe gesture from left to right (like Gmail checkboxes) to activate selection state
• Multi-touch gesture (two fingers) for range selection — although possibly confusing

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Drawbacks

• Implementing touch gestures in a tree view UI can be tricky and might conflict with scrolling behavior
• Needs careful UX design to avoid accidental selection

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Implementation Notes

• Could be limited to touchscreen platforms using OS.has_touchscreen_ui_hint()
• May require extending the SceneTreeEditor to handle gesture events
• Should preserve full parity with desktop multi-selection behavior

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What do you think? I'd love to hear feedback or suggestions from others using Godot on mobile!

[syntaxerror247]

Multi-select is already possible in godot 4.5 using TouchActionsPanel. It has a button to toggle ctrl key and then you can tap anywhere, it emulates ctrl+click behaviour. See https://godotengine.org/article/dev-snapshot-godot-4-5-beta-1/#android, there's a video showcasing multi-select in Android Editor.