DEV: do not process composer preview when collapsed (PR #13941)

Note that I would prefer to not use the observer but that would end up being a way bigger and risky refactor.

GitHub

I’m curious, what happens if you hide the preview and then post?

Observers are OK if they really simplify things. At the very least we can delay moving away from this one.

I’m curious, what happens if you hide the preview and then post?

Does the cooked post look good in the stream?

yes it works in my tests