Hi Mark,
I don't know anything about B.I.A.B, but Yamaha MIDI Setup files also have the extension '.msu' and I suspect that your file is one of these!
Although you can edit and save MIDI templates on your Genos, as you have discovered, they can only be saved to the User drive.
However you can then use the 'Factory Setup/Restore' function of the 'Utility' display to save (and load) all of the user MIDI templates together as a single file. This produces the MIDI Setup file with the '.msu' extension. It can be saved to, and loaded from, either the User drive or USB.
However you need to be a bit careful!
Bear in mind that when you load one of these '.msu' files, you will be overwriting all of the user templates currently in the instrument (there is a warning!), so if for example, you have saved any additional user ones since you saved the setup file that you are about to load, you will effectively delete them! It is probably prudent to always save the current user MIDI templates in a Setup '.msu' before loading a different one!
There is a note about how user MIDI templates are saved like this on page 143 of the downloadable 'Genos Reference Manual' which says:
"Your original MIDI templates can be saved as a single file to a USB flash drive. On the display called up via
[MENU] > [Utility] > [Factory Reset/Backup] > page 2/2, touch [Save] of “MIDI” to carry out the Save operation"
Saving and Loading MIDI Setup files is explained in the section 'Setup Files—Saving and Loading' on page 159 of the same manual.
Regards
Ian