Thanks for playing ! Although it is possible to make level like this using gridmap3d, I did not use it. Most geometry was made in godot, exported to blender and retextured and reimported. placement of objects was done by measurement of modules and placing them appropriately.
I have added more content to the game and some bugfixes, I did not use gridmap3d node but I placed most meshes and all scenes and stuff at a very close integer values as much as possible, if you'd like, you can give it one more try.