Sometimes, you need to just focus on writing and you do not want to see any visual clutter. You can close sidebar however you cannot hide topbar (with format, info (backlinks, outline…) and name of the note when scrolling down). I believe it could be set to hidden/visible or even visible only on hoover etc. (The three dots could stay)
Hiding topbar (and typewriter mode) would be killer issues for uncluttered writing.
Just so long as what you are proposing isn’t the default behavior. Having the top bar hide when you scroll down and show when you scroll up is very distracting for me. I see differences and that top bar hiding and showing makes my attention fly right to the top bar.