To see the forum while composing, you can still use the dedicated minimise button in the top right corner.
There may be potential differences in experiences between Hub/webapp, or the various browsers. Please report those to see if this is a viable change everywhere or not.
Maybe it’s just me, but I prefer having the composer at half-height when the keyboard is closed, as I need to quote different things from a post above, but this makes it harder - I have to collapse the whole composer instead.
On a smartphone, things look good to me. However, on tablets, I am less sure.
First, when I start a reply, the composer area is quite small (screenshot from a 12.9“ iPad below), definitely smaller than it needs to be.
But when I enter the text box and start typing, the composer goes fullscreen as for my iPhone, which is not really needed IMO (and there’s also no obvious means to resize it to half size - which is probably intended).
Yes, the tablet experience is lacking atm and has a whole bunch of other things “going on” that I need to look at to optimise things. It def needs a different approach.
Would it be possible to have the option for both? I like the full screen for reading back, but I also like the half screen for inserting quotes and comparing my answer to the post I’m replying to. At the moment, when I minimise it places the cursor to the end of the composer text, and pops the quote there (when I wanted to put it mid post).
Could I have a button that toggles half screen/full screen (& minimise)?
I like the half-composer for this too. I like the option of having both my bit and the thing I’m replying to next to each other without having to flick between screens. I think it helps me double-check what I’m saying is relevant and I’m replying to what was said and not just what I think someone said [1]
Edit: Just realized that this is by design and, according to the quote below, “experimental”.
In that case, it would have been a more graceful solution to make it opt-in only via site settings, just like any other experimental feature, and not force it upon all users.
I wish someone could come up with a workaround plugin or a hotfix to bring back the split-view composer.
I didn’t realize this change was intentional, but it makes the experience on mobile significantly worse for me. Why does the composer need to be full screen to review what you wrote? There’s already a preview button for that which does the same thing but better. Now it’s much harder to check what I wrote against the post(s) I’m replying to since I can only see my text (full screen composer) or their text (minimize the composer), never both at the same time.
I experimented a bit with building a Theme component that basically renders the cooked post I am replying to, right above the composer. But that didn’t really cover the use case when I want to quote text snippets from multiple posts in a subsequent manner.
I would rather have a non-fullscreen adjustable composer text area which then expands with each consequent line break.
When replying, opening an empty composer in full height is definitely not the best use of the very limited space on a smartphone. See screenshot below and the red marking.
Yeah I like it too. Thanks 
