I left the material on CSGMesh because GeometryInstance's material override prevents the normal material behaviour of the csg meshes
but the material_override is useful, and now you can control the shadow, lod and other properties you get from GeometryInstance
-Missing Icons
-Missing freezing option (for baking light and faster load)
-Missing a way to export from Godot (GLTF2?)
-Probably buggy (may freeze editor, can be worked around easily, but let me know if this happens so it's easier to catch bugs)
Happy testing!