What I was thinking of are called rocker gestures, though don't ask me where that term is from, because I can't remember .
I'm thinking of holding down the right button and then pressing left button, or holding down the left button and then pressing the right button.
Hmm, I think firefox gestures are where I used these last.

The way the dialog is now, these will be possible to create. It's just a nice option to have.