"X3 now has full support for mono sidechainable plugins for both VST2 and VST3 (e.g. Fabfilter Pro C – Mono SC, Waves C1 comp SC mono, etc)"
 
I'm trying to get sidechain working with tonebooster TB_Compressor.. No luck
The plugin do support sidechaining,but I do not manage to route a track to the sidechain input (nothing appear in output)
 
Any Idea?