Syncing them with program changes is pretty straight forward.

On the OT go to project / midi/ sync select send clock and transport. Go to PROG CH and select send and a channel. I have 9.

On the A4 got to global / midi config / midi sync. Select clock, transport and prog ch receive.

Go back out to A4 midi channels and assign PROG CH IN CH to 9 or whatever you used from the OT.