Apply vertex displacement to GeometryInstance

[DxUr]

Godot version

4.0.3

System information

N/A

Issue description

I cant apply a vertex displacement to a GeometryInstance (MeshInstance) without affecting the materials (override the entire material) , and it's imposible to use a custom shader to each surface for each GeometryInstance in my project, if there is just a little idea of how I can solve this just tell me , I'm using C++ in my project so I dont have any issues with compiling custom engine build.

Steps to reproduce

N/A

Minimal reproduction project

N/A

[Calinou]

Please don't ask support questions here, as this issue tracker is meant to be used for bug reports only. Use one of the other community channels instead.

See also godotengine/godot-proposals#1779 and godotengine/godot-proposals#2595.