Olle on Separating the snare and the side stick?

You would have to Add the same snare as a new Instrument (X-drum).
Then you would deactivate all its articulations except the SideStick and
assign the proper MIDI notes to it. In the normal snare you would then
deactivate the SideStick articulation. Then you route the mics of the
new snare to your liking, probably creating a few new mics in the mixer
in the process.