Sidechaining instruments in Artist 11

I saw a video where the guy set up Retrologue as a send on a track and then went in and set RL to side chain so he could use the RL filter and fx
even though the track was not made by RL. Can you do that with any other vst instrument you have like Avenger or Halion…?
and how did he have Retrlogue show up on his send choices?