I updated the CopyAsNewFurniture plug-in was updated to version 1.3 to handle the copy of
- furniture groups,
- standalone rooms (only if at an upper level),
- furniture elevation at different levels,
- texts visible in 3D,
- polylines visible in 3D.

Therefore, if you select all at all levels (and possibly unselect a few items after that), this plug-in will copy the selected items respecting their global elevation.