Thanks for your reply, but my question was how to do it using the Library Part Maker add-on.
A window object created using slabs in the way you described is not suitable for two reasons. First, it does not react to the side materials of the wall, so the opening on both sides of the window frame receives the material of the wall edge. Second, when such a window is at zero floor level, the Zone does not respond to it when calculating the area of the room.
In the meantime, a window object created using the Library Part Maker add-on shows everything correctly. However, the LPM User Guide does not explain how to make a custom-shaped wall hole instead of an automatically made rectangle.
Guys, does anyone use LPM to create objects?
Could the developers of this add-on answer my question?