tbh. personally, i'm no fan of this technique, if i ever tried it once at all. so you may find that the internal qtractor routing design is not that (well) suited for it. however, Jeremy is one big qtractor power-user, no doubt. he even knows (and uses ways of doing) things that i wouldn't dimmed possible if i were to think about it:)
hi Phil,
there used to be a video tutorial for just that on yt, all credits and thanks to AutoStatic (Jeremy):
Tiny Tutorial: Sidechain Compression in Qtractor
tbh. personally, i'm no fan of this technique, if i ever tried it once at all. so you may find that the internal qtractor routing design is not that (well) suited for it. however, Jeremy is one big qtractor power-user, no doubt. he even knows (and uses ways of doing) things that i wouldn't dimmed possible if i were to think about it:)
cheers