[Led]

The only sad roundabout way I do this is to highlight all the send tracks plus aux track, hit shift+alt+solo, which solos them all, then set the send tracks to 'no output'. Works ok with only a couple of send tracks, takes more clicking around for something like a whole kit, but you can highlight all send tracks and hold shift+option to change all their outputs at once. That way you are still hearing the aux return via any buss processing.
It's such a helpful thing to be able to solo aux returns for layering them eq wise, bit of an oversight imho.