SceneTreeDialog: better navigation for large scene trees

[RedMser]

Describe the project you are working on

Game with large scene tree

Describe the problem or limitation you are having in your project

A note on terminology: In the following sections, "originating node" refers to the node from which the NodePaths are relative to. It is equivalent to the node that you opened the selection dialog from:

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We use a lot of @export var x: Node etc. in our code. Our levels are large scene trees with a lot of nodes in them.

When opening the "Select a Node" dialog, it's hard to orient yourself, since it starts scrolled to the top and the originating node is not highlighted in any way:

Describe the feature / enhancement and how it helps to overcome the problem or limitation

• Scroll the tree view so that the originating node is centered in the view.
• Highlight the originating node, so it is easier to e.g. select a child or parent node.

Describe how your proposal will work, with code, pseudo-code, mock-ups, and/or diagrams

Here I used the "Override" icon with 50% opacity to highlight the originating node. The dialog also starts with the scroll bar at the bottom.

If this enhancement will not be used often, can it be worked around with a few lines of script?

No, this is a UX improvement.

Is there a reason why this should be core and not an add-on in the asset library?

Can't be add-on.

[RedMser]

My PR's implementation differs slightly, as the SceneTreeEditor already features a set_marked function. Instead of using an icon, it changes the text color of the item.

An additional change was to properly set and clear the node selection, as this was previously not implemented properly. Selection takes priority over marked nodes when it comes to deciding where to scroll to.