Describe the project you are working on

2D Shooter game with minimap which uses SubViewport and visibility_layers

Describe the problem or limitation you are having in your project

Minimap works this way: all its elements are on visibility layer 2, and everything else by default is on layer 1. I have MinimapViewport which have canvas_cull_mask set to 2. And I need to hide all CanvasItems with layer 2 on the root Viewport. To do this, I can write some initialization code, like get_tree().root.set_canvas_cull_mask_bit(2, false), from editor interface I can't do this.

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

Add project setting rendering/viewport/default_canvas_cull_mask which sets canvas_cull_mask on root Viewport on startup, providing more friendly interface than editing in code.

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

Just single project setting rendering/viewport/default_canvas_cull_mask, which sets canvas_cull_mask on root Viewport on startup, but only in Game, not the Editor (I want to see all CanvasItems in the editor regardless of this setting)

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

It can be worked around, but we have so much settings which just set something on root Viewport on startup, so, why not?

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

It's core