Old behavior (Renoise 3.0):
Having defined an instrument with an effect chain routed to “track”, it would play back that instrument and feed it to the currently selected track. When the user would select a different track, the effect chain destination “track” was updated immediately. Live playing of that instrument would directly feed to the currently selected track.
Renoise 3.1:
The effect chain routing destination is now named “Current track”. The value of “Current track” (the track it is pointing to) is only updated after a “programmed” note (a note part of a pattern, as opposed to a note played live via a controller or keyboard) for the instrument has been played on a track. The track that “Current track” points to then becomes the track containing the last played note for that instrument.
For live playing I would strongly prefer the “Current track” value to be updated at the moment a different track is selected.