I’ve had a few people ask me questions that show that fill tracks are not as well understood as they ought to be. There are some quirks in how fill tracks work differently to the main beat of a part.
This video explains them a bit more, and how you might use their differences to improve your songs.
Let me know if you still have any questions.
Super useful feature! 
Does this apply only your BBFF Editor or also BB Manager? 
It is extremely difficult to do in BBM
To get the fill accent at the end in the BBM MIDI editor, you need to add a bar, add the accent beats, and then remove the last bar.
I’m not actually sure how to do the fill offset in BBM
I think I have done this, or something similar in BBM
So it’s a file format that the BB supports, but BBM not necessarily? 
Initially I thought that it’s just some easy to use feature of BBFF Editor, but not really embedded in the file format 
But I suppose it’s still part of midi, right?
It’s a bit complicated. It’s not really part of the MIDI format (which is just a sequence of notes/beats in time) but about when those beats stop/start.
The thing that makes it unique to the BeatBuddy fills is that the main beat should still continue playing and the fill needs to start at a specific point and only then should the main beat stop.
As an aside, the BeatBuddy also uses fill choke groups (different to normal choke groups that are often used in MIDI percussion) in it’s instruments (drumset editor) to make sure that the beats in the accent portion of the fill don’t collide with the first beats of the main beat.
…it’s just some easy to use feature of BBFF Editor…
Easy to use was my aim 