Is there a way to "insert" a floor into a pre-existing building?

"ReflectedLight;d-969543" wrote:
Hello. If I see a lot that the roof is rather complex, made up of many different parts and objects, and it's not as easy to delete it, build a new higher level floor, then re-create the roof again, is there a way to keep the roof intact but insert another floor to the building?

Thanks in advance!