Does anyone know if there’s a way to do a factory reset on the MIDI Maestro, or do I just need to go into my custom mode and delete all the messages/commands, or maybe start a new blank custom mode? I just want to figure out how to reset it for a new owner.
I’m not aware of a way to do that either. Back in the day when I couldn’t get blank pages to fall off, I created a “blanker” mode. I think that’ll be faster than going page by page.
Like b0n3 say
Make a new custom and start with “Blank”
Than you can click the trash icon to the other and delete it
I ended up creating a new custom mode and used “blank” as the template. That seemed to work to get it as close to “factory new” as I think is possible. 
Would reflashing the firmware clear the memory? A few of my older synths would lose user stored settings when their firmware was updated or reinstalled.
I always ran the firmware “update” and then the default modes “update” whenever I logged into the app, which I did this last time as well. My custom mode always remained after “reflashing” the firmware.