In the current version of Superior Drummer 3 (Superior Drummer 3 plug-in version 3.3.6 (build 35757) [64-bit VST 2] / Standalone host version 3.3.6 (build 35757)) :
When the metronome is on, if you solo any channel on the mixer, then it mutes the metronome (because it’s not a solo-ed channel).
This sucks because sometimes you want to hear the metronome but be able to audition only certain channels by solo-ing them, and you don’t have the metronome as its own channel so you can’t solo it to be able to hgear it alongside other solo-ed tracks.
It would be nice to have the metronome have a “solo defeat” behaviour by default, which means you can still hear the metronome even if you solo any channel(s) and the metronome is turned on.
If you don’t want to hear the metronome, you just have to turn it off.