This is a pretty slick app! One thing I notice is that there are a lot of options in things like the insert menu with tags that aren't super popular. Maybe prioritizing more commonly used options would help with the UX? Also once you're logged in, there's no way to get back to the landing page without logging out.
Also, is there a way to make more than one project/rename projects? Another UI thing, I think having those side panels expand on hover is a little distracting, maybe use a chevron to expand/collapse? If you have contact info on the page I'd be happy to give some more feedback, don't want to spam HN
