I suggest renaming the models, for example in the /Floor/ folder, all assets get the same name!
What's happening? Well, the mesh library will only import one of them.
Before:
The solution is to take each PacketScene in /Floor/ create a new inherited scene from there and rename its MeshInstance3D.
After:
If you see this
Its name is in yellow, to edit it, you can select its root node and select "change type" you can choose the same type "Node3D", but then you will be able to edit the scene. Don't forget to save each scene and use it.
To explain better I will use a StaticBody3D root node in each scene
now when export the scene Floor to mesh library...
The end result is all the floor parts in your own .meshlib.
I suggest renaming the models, for example in the /Floor/ folder, all assets get the same name! What's happening? Well, the mesh library will only import one of them.
Before:
The solution is to take each PacketScene in /Floor/ create a new inherited scene from there and rename its MeshInstance3D. After:
If you see this Its name is in yellow, to edit it, you can select its root node and select "change type" you can choose the same type "Node3D", but then you will be able to edit the scene. Don't forget to save each scene and use it.
To explain better I will use a StaticBody3D root node in each scene
now when export the scene Floor to mesh library...
The end result is all the floor parts in your own .meshlib.