If your rectangle size is set to the A value then you actually dont need to use moveable hotspots. The standard “hotspot2 A, 0” will be movebale. its one of the nice efficiencies in Archicad that is very helpful when creating windows and doors.
So an editable rectangle (with bottom left corner as 0,0) would simply need the following 4 hotspots:
hotspot2 0, 0
hotspot2 0, B
hotspot2 A, B
hotspot2 A, 0