Modulate pan from within track
It’s possible to modulate pan from the master track but not from a track’s audio output module.
From the master track it’s possible to modulate track 2’s pan from a module in track 1.
it’s not possible to modulate track 1’s pan from a module in track 1. This can’t be explained by a pure right-to-left, top-to-bottom rule since the output of track 1 is the last module in the track so should be modulatable by any module in the track.