In Cubase 13 (running on MacOS) I had the preferences set such that clicking on the edit channel button on a track in the stand alone mix console window did not cause the track to be selected. This still seems to work if I disable “Select Channel/Track on Edit Settings” under “Project & Mix Console” in the Editing preferences for Cubase 15.
It also worked in Cubase 13 to deselect 1 or more tracks by clicking on the empty background in the mixer. But I don’t see what settings that corresponds to in Cubase 15 on order to reproduce that behavior from Cubase 13.