Sorry, my bad. I guess I mixed it up with a Microstation Triforma technique - there any 2D polygon would do to designate the hole cutting shape. It was a long time since I made a custom window in Archicad.
But the 3rd dimension of the slab isn't really used, is it?
I have always just used the custom door option and create my door from slabs, and since I usually have a thickened wall at the garage, I put my square carriage style door in the back wall, and my arched, or custom opening in the front wall. Since I started using the US library SE, I can't seem to get the garage doors to show my custom panels, is anyone else having this problem?
I have re-saved new instances (with "10" added to the name) of my doors from the AC10 3D window. Yet the doors saved as library parts in AC9 and the doors saved in AC10 "act" the same. They are placed Outside the wall. See Attachment.