You can go with an insert in a qtractor output bus. All tracks that are supposed to share a bus insert plug-in must be assigned to that same output bus.
In case you didn't notice, qtractor output buses are in fact mix-down devices that can hold a plug-in chain and send/return inserts as any individual track.
One simple restriction you might find is that one track can only have one output bus and that's a designated fact :) Another one is that, due to qtractor internal process, it's of no consequence if you connect any qtractor audio output bus directly to one of its own input buses--you should use an intermediate JACK client for that to work at all, that is, to have any signal go through the loop-back.
Take a look at page 14 of the ageing user manual. There you'll find the evil flow/block diagram that should explain a bit the routing innards of qtractor signal flow (also shown below).
You can go with an insert in a qtractor output bus. All tracks that are supposed to share a bus insert plug-in must be assigned to that same output bus.
In case you didn't notice, qtractor output buses are in fact mix-down devices that can hold a plug-in chain and send/return inserts as any individual track.
One simple restriction you might find is that one track can only have one output bus and that's a designated fact :) Another one is that, due to qtractor internal process, it's of no consequence if you connect any qtractor audio output bus directly to one of its own input buses--you should use an intermediate JACK client for that to work at all, that is, to have any signal go through the loop-back.
Take a look at page 14 of the ageing user manual. There you'll find the evil flow/block diagram that should explain a bit the routing innards of qtractor signal flow (also shown below).
HTH