Thanks for the script.
I have tried it out. I have got the script to work but I am not sure weather the midi files will be useful for EZDrummer.

I think I need midi files that only contain the drum track in order for it to be useful in EZDrummer. When I export an MGU as midi from Biab I got a midi for the whole song, all instruments, not only the drum track. And I have not found a way to import only the drum track from the midi to EZDrummer. It seems to import all midi instruments in the file and it makes it a very messy drum track (maybe there is a way I have not found it).

Also when I was inspecting some of the MGU files in BIAB, they have no drum sound on the drum track or other instruments even though they are populated with RD and RTs. All instruments seem to be held in the melody track and the rest of the instrument tracks marked as frozen, so it will not produce any individual instrument midi tracks on export.

(Anyway I got the script to work after some trouble shooting. It did not work as is on my PC, Windows 11, Biab 2023 Build 1013 64B, AutoHot Key 1.1.
Not really sure what I am doing I have never used AutoHotKey before. But the scrip seems to work now (it will break the loop if a style is missing for the MGU but otherwise it seems to work).
I had to make the following changes
Add SetControlDelay -1 before the ControlClick and ControlFocus statements
;SendRaw, %subdir% did not work replaced it with
Send {Text}%subdir%
;Send, !o ; did not work replaced it with
Send, {Enter}
)

I leave this for now , thanks for the script. I have learned a lot and have a skeleton script I might be able to develop further for other things.