Thanks for that! Very cool.
Essentially, it lets you work up a drum groove with clear beat divisions, a variety of beat subdivisions, 1/8, 1/16, triplets, etc., and it has a SWING setting so you can adjust the amount of swing. You can export the groove as midi track and import it into a BB song.
Downside - as best as I can tell, it only has 5 drums available, kick, snare, hat and 2 toms.
Upside - It’s a heliuva lot easier to use than the BB midi editor, and it’s free.