How do I add commands to Touch Bar for iMovie?

I've recently gotten a 16" mbp, and I've been using iMovie with it lately for different projects. On the Touch Bar, the only command I see for iMovie is "split clip." I'd like to add a "Detach Audio" button for now, but as a brand new BTT user, I'm a little overwhelmed by the interface and need some help.

Can anyone offer me some help or a suggestion here?