Using BTT and Touch Bar with Drafts?

I like to draft emails in Drafts for Mac OS, and send them to Mail from there. There's not a keyboard shortcut that I can find for that (I have to navigate through the menu or use the trackpad), but if I could have a button in the Touch Bar that I could us, that'd be great.

How do I manage that, though, without having a keyboard shortcut to link it to?