Implementare in modo coerente l'overflow degli elementi della barra degli strumenti di composer

[awesomerobot (Kris)]

@sam

An alternative here is… as stuff gets too narrow, shift them behind the + by a priority.

This feels like the nicest approach to me, we could also use reuse it on posts with the ... menu — but scrolling is certainly simpler to implement as long as we figure out how to make it obvious