Hi Lennard,
I am trying the same thing on 5.1.1., I didn’t dig very deep but it basically seems to work using the same sync-group name.
I’ve tried most settings and setting the external BS to “always leader” in the sync-group section seems to give the best results.
Also maybe this makes a difference (maybe not) - in the main graph from which I go into the external animBP in the LinkedAnimGraph node I’ve checked these properties
[x] Receive Notifies from Linked Instances
[x] Propagate Notifies to Linked instances
The problem I couldn’t find is (independent of external or internal BS with sync-group) is that I sometimes get a phase jump. e.g. when going from a walk-cycle with 3 different cycles to a stop or turn using the same sync-group doesn’t always start from the beginning (even when I check reset on entry)