Just to reflect on your "wish": yes, it would be nice, even more so since this intelligence is there within ArchiCAD.
Currently one could do it in a workaround way by making the subtype of these elements to be a Door or Window type since you can place a Door or Window only into a Wall.
I am only saying this to illustrate that ArchiCAD already has the intelligence to be able to find and snap to surfaces of other elements.
The other example of this is the Gravity feature where you can place elements to the top surface of Slabs, Roofs and Meshes.
Why not have an "anti-gravity" feature which snaps elements to the bottom surface of Slabs or Roofs or Beams or any surface for that matter.
So maybe the solution would be the extension of the Gravity feature, only you would not call it gravity. Certain element types could only be placed onto Walls or onto bottom surfaces of Slabs or whatever.
I would love to see such a feature in a future version.
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