Sounds like you may be trying to place a complex profile wall rather than a standard or composite wall.
With complex profiles it is only left or right.
You should add your Archicad version to your post - preferably add it to your profile signature along with your operating system and maybe even machine specs.
The profile link is at the top of the forum page.
This is a request not aimed solely at you but all posters on this forum.
Archicad versions, OS, etc., can sometimes affect the answer to your questions.
i.e. wall reference lines have changed slightly in 17 - can now be relative to the cores and not just the overall wall - not that it will affect the answer in this case though I don't think.
Barry.
One of the forum moderators.
Versions 6.5 to 27
i7-10700 @ 2.9Ghz, 32GB ram, GeForce RTX 2060 (6GB), Windows 10
Lenovo Thinkpad - i7-1270P 2.20 GHz, 32GB RAM, Nvidia T550, Windows 11