I have this issue too and overcome it by using the "Export" function in Cisco PI.
Once exported I then renamed the existing Floor Name and Number to something else (the floor you want to duplicate).
Then I ran the "Import" function to import the file saved earlier.
During the Import process the key here is to NOT Overwrite (uncheck) the Message containing "Building 'building_name' exists and will be overwritten"
This will result in an additional floor with the same floor plan and obstacles applied.
I repeated this process for all floors in the building that have the same/similar floor plan and obstacles.
