It's used to drag and drop a song into your DAW. So you make a BIAB song, then drag the "combo" to the "Drag and Drop" area. Once the song is generated, the drag and drop region will turn green. Now you can invoke DAW mode, which will make BIAB shrink down small on your screen. Then from the green "Drag and Drop" area, you drag your song into your DAW (like Garageband or Logic). It's best to set the tempo and song key in your DAW prior to dragging into the DAW. Now your DAW program will create a track for each BIAB track, and all the BIAB song is now in your DAW program. Try it - works like a charm for me! Once you're done with this, you can quit DAW mode, and BIAB goes back to it's full size again.

Bruce

Macbook Pro 2018
2.6 GHz 6-core Intel Core i7, 16 GB RAM
OS Monterey
BIAB for Mac 2022