Copy/Paste a Group

OK. I think I see what you are trying to do. In the file you posted, select both the exterior and interior wall plan groups.and hit Ctrl+C to copy them to the clipboard. Then to make it easier to see what you are doing, uncheck the Walls - Interior and Walls - Exterior layers to turn them off. Hit Edit>Paste in place and then immediately, in Entity Info, set their layer association to Plan 2D.