You could import and use one or more large invisible boxes to cut the walls they will intersect, as in the file attached to this post.
Don't forget to select the Door or window at the 3rd step of the import furniture wizard, and then disable magnetism when you move the box so the program doesn't try to place the moved box on the closest wall. Note that those boxes will cut only walls and not other doors and windows, and if you import an invisible box as a staircase it will similarly cut all the floors.