FLStudio 12 (Producer Edition) with the plugin Fruity Send:
-By default, the 'send to' track is 'Master' , or '1'
-Upon changing this to a different target track, it will send to the appropriate channel just fine
-However, this setting ...
FL seems to treat this as a potential mappable input. So if you click the Multilink knob, it is instantly disabled with the error "You didn't tweak any control"
So this requires using the browser to find ...