My take on this. It really depends on what you expect to hear, sorry if that sounds condecending, what I mean is are you looking for selected channels as part of the output mix (Post Fade) or simply multiple inputs at pre fade that will be unbalanced at input gain levels?
1. For stereo, post fade, thus something near output mix of selected channels. Best way I can think of without getting the gear out, create a linked pair of auxes, then send the prescribed channels to that aux pair using the send sliders. As its a stero ouput then hopefully the sent channels will be either mono panned out as of its main send, or as a stereo channel etc.
2. Mono would be the same setup but just the one aux
In both these cases you need to set the aux channel(s) to post fade, same as if you were using for external FX send as I do to a vocal processor module.
There is no button option to do this im afraid as the CQ does not have any SOLO function.
Hope this helps.