This topic is still unanswered an is very crucial to be able to manage seamless animation flow between montages launched from code and back to the ABP.
As of today this is still not working (I’m using UE 4.26). Documentation doesn’t clarify this topic enough, just said sync with syn markers on blend out is available on montages. But in every little post you find about this topic all users agree that this is not working. So one of this two:
1 - Everyone out there asking has no idea how to properly set up this, so the proper way to do it is tricky and is not covered in enough detail in the documentation.
2 - The feature doesn’t work.
In case it works, in addition to all this it isn’t clear which role the montage is assuming in the sync (In the example OP was talking about with a montage for a walk start/stop transition animation, you will want that the transition be the leader and the walk cycle in your ABP be the follower). How you know which role the montage is taking? Is it possible to change it?
If someone can give light to this topic it will help an example of how to setup one case like that start/stop walk montage > walk cycle.