Crop to Single-Plane Roof

You can still use the old method of cropping the walls to a single roof, used mainly to trim walls in an angle.

If you are working in ArchiCAD 18 or older you already know that you can right-click the wall and crop the wall.

However, if you are in ArchiCAD 19 or a newer version you will find this menu if you select the wall and go to the menu Design>Roof Extras> You can either crop to the roof or undo the crops.