You are correct ofc about Transpose + Yes, but the main thing here is that op achieved a desired workflow and there is less “limitation” than initially perceived.
so if I understand correctly, if I want to transpose only one of the 4 tracks;
the easiest way is to lock the other three first (transpose + yes)?
and then use transpose on the track I want to transpose?
No, you transpose only the track you want to. But it is temporarily, so if you turn transpose off, it will revert to original values. To avoid that hit transpose and yes, to apply it permanently (change the actual note Values in the sequencer). After that this track will stay transposed and you can select other tracks to transpose…