Writing requires focus, which is why I’m a big fan of distraction-free editors (see my review of Typora, for example). In that spirit, I’ve added support for full-screen editing to lib.reviews. Here’s what it looks like (if your browser window is tiny).
Note that technically this is full-window editing rather than full-screen editing. This is intentional. My assumption is that in most cases, users will still want to have easy access to their other tabs and windows. But you’re in control: if you want to get rid of everything else, just switch the browser into full-screen mode, as well (F11 in Firefox or Chrome).
This mode should also help with larger reviews with lots of images that benefit from the additional screen real estate.