In my opinion, the multi-storey use is not fully developed (even with 2 floors). As far as I know, you can only save one plan with room division. For the 2nd floor, I deactivate the mapping function and just let it go. This actually works quite well, but for me it has nothing to do with multi-storey use... You have to remember to switch off the mapping function, otherwise the saved maps will be overwritten (not recoverable...).