Please read this thread about using the Merge Wall feature for this function.
http://archicad-talk.graphisoft.com/viewtopic.php?t=27230
It can work, but not if the reference lines are offset, so this wish is still quite valid, but the other thread should be read by anyone wanting to use the Merge Wall "trick".
Cheers,
Karl
One of the forum moderators
AC 27 USA and earlier • macOS Ventura 13.6.6, MacBook Pro M2 Max 12CPU/30GPU cores, 32GB