Short answer: The bus is either A) connected in the i/o setup window’s “Bus” section to an output (outputs are defined in the same window’s “Outputs” section which shows interface outs), or B) it is ‘chosen’ as an input to something else - an audio track or an Aux track for example.
You can think about ‘the bus’ as a floating wire that can sum things. You can connect things “to” the ‘top’ of that wire, and at the end you can either choose a destination (“A” above) or you can select the end of the wire as an input at one or more other points. The Master Fader as you pointed out simply sits ‘on’ that wire, at the end of it, taking the summed signal and gives you some controls over it (inserts, fader).
When I think of Cubendo I think of a “bus” as always having controls associated with it. Functionally, practically, a Group Track and Output Bus in Cubendo are quite similar in this sense (or identical).
The way it looks to me - which I just tried in PT - is that all that he’s doing is that he’s extending the amount of inserts he has in a row by using that Master Fader on the bus. All that seems to be happening is that the outputs of the drum tracks in question is into the “C DRUMS” bus which has a bunch of inserts on it (using the Master Fader), and then that bus becomes the input of “C DRUMS” Aux track which in turn has more inserts on it. It just looks weird but to me it just looks like a bunch of processing in series.
All you would have to do is ‘stack’ group tracks if this is what you wanted to do. Your first group track would be “C DRUMS M” (to which you would output your drum audio tracks), and you would have it go to a second group called “C DRUMS”, and from there to “ALL DRUMS”. That’s it.
Unless I’m missing something…