I don't understand it In the video there are INSERTs used instead of AUX. You can have the same effect with duplex buses and using their input bus. You can connect anything to anything if you use duplex buses or INSERTs for the price of adding one jack buffer of latency. Keeping latencies equal for all tracks is key. See https://sourceforge.net/p/qtractor/wiki/How%20To%20-%207%20Equal%20Latency%20for%20Tracks%20and%20Buses/ Reply
In the video there are INSERTs used instead of AUX. You can have the same effect with duplex buses and using their input bus. You can connect anything to anything if you use duplex buses or INSERTs for the price of adding one jack buffer of latency. Keeping latencies equal for all tracks is key.
See https://sourceforge.net/p/qtractor/wiki/How%20To%20-%207%20Equal%20Latency%20for%20Tracks%20and%20Buses/