Oh... See! I would've done complete nonsense if I hadn't asked. ☺
Well, this then is actually a completely different story, indeed. This requires adding an UI element, rather than changing present ones. In fact, it would be reasonable to leave it out of the core overall, as it's matter of taste whether you would want to use it or not.
Are you familiar with the template engine used (templates.js)? I'm not much of a UI guy and if you used it before, I would guess you are familiar with buffer-buttons and how to embed them (HTML/CSS). Maybe you could place those buttons in the (your) theme and I'll provide the needed data from the backend (i.e. plugin).
I really gotta sleep. 😕 Needed like 10 minutes for those few lines now. xD
But I'm pretty confident, that this is not too complicated, after all!