girts:
The Object can be converted to Morph, then edited in the 3D Window, but this will loose the parametric features of the Object. A parametric Object needs to be scripted, not edited in a 2D or 3D window.
You should add a Signature to your Profile (click the Profile button near the top of this page) with your ArchiCAD version and operating system (see mine for an example) for more accurate help in this forum.
David