How to have specific scene visible in BG in other scenes

Godot Version

4.4

Question

I have specific scene with some animations. My other scenes have some semi-transparent textures/nodes. So i want my specific scene to be active and visible as bg (as much as it can) in all other scenes regardless where/when they are. I want something like environment->background color in project settings but its node version.

What i think as one of the solutions is, having only one major scene in the viewport all the time and other scenes will be added as child (not replacing major, only replacing children). But i dont know how to manage that