i have made some similar objects by modifiyng the archicad wall-accesory
object, to put only a beam at top of walls and doors & windows
and not the entire wall wood frame.
I also derivated other roof accesory objects.
the addon (*.apx ) only put the corect values in object parameters (coordinates, etc) but all the accesory objects are just objects - gdl
depend of you needs and imagination to put at work the apx capability to give automate values to this objects.you must study the archicad original gdl code and try to modify . ( ac_coords... etc) you will see..
dont forget to save by correct subtype library .
if a skylight object is not saved as skylight subtype it will not work because the skylight.apx will not recognize them.
in your particular case i sugest to keep only the base beam of
"Wall Framing.gsm"