Found a bit of a bug between showing/hiding tracks in a folder in the mixer and OnFXFocus MapFocusedTrackFXToWidgets.
If the tracks in a folder are hidden in the mixer, FX on tracks after the folder track (but not in the folder) won't map when focussed.
If you show the tracks in the folder (with that little clickable circle on the bottom left of the mixer channel) the FX behaviour returns to normal.
Regarding folders, it's a shame we've only got: Toggle show tracks in folders in mixer
If we had: Toggle show tracks in folders in mixer on selected track(s)
We'd be golden
