This is slowly coming together.
I had to do a fairly large refactoring of the transport control mechanism, but that’s mostly in-place now - as is a new sync mode setting, a state behaviour for sync mode and most of the UI related bits.
When a player is synced, it’s transport controls disappear when it’s stopped and fade out when playing or paused. Also, there’s a little link icon to indicate it’s synced and a new context menu popup to set the sync mode.
Basically the framework is in place and synced players now start and stop with the master. The main thing left to be done now is syncing the transport position and timing information.