Nice looking software!
I guess if it weren’t available, routing the track or project to a group, and then A/B’ng that group with the commercial track would work OK for the bare bones aspect of the whole thing (using the “Select both, Mute one/Solo the other, then toggle with the ‘M’ key” technique). But the other bells and whistles would be missing of course.
Now that I’m more comfortable using the control room the way I described, I do think when I get to mixing next I’ll try and see how the same technique works for quick A/B of different mixes (or A/B/C/D/E, since there are four Studio Sends … maybe?!).