these are some things you have to know about qtractor under-the-hood workings ;)
all plugin processing and routing is internal to qtractor;
you won't ever see any plugin ports exposed to the outside, exceptions made to the insert Send/Return and Aux-Send pseudo-plugins;
only buses present audio/MIDI ports respectively to the outside;
when inserted, each audio/MIDI plugin port is mapped 1:1 and routed internally in qtractor track/bus;
all this internal routing is done seamlessly for input and output and inter-chained plugins, provided that plugin audio and MIDI ports are declared in conventional order (eg. first audio port is left channel, second is right channel).
these are some things you have to know about qtractor under-the-hood workings ;)
hth.
cheers