writ.ly
I've also modularized the editor (https://github.com/writly/writly) as a React Component. Feel free to give it a try!
It would be nice if you could change the block type after creating it. For example I don't think there's a way to change an h1 to an h2, or a bulleted list to a numbered list.
The collaborative editing is neat too, are you using a library for that or is it bespoke as well?
Most of the heavy work, including collaborative editing, is done with Facebook’s Lexical library. There’s also a Vue binding for Lexical, so you should try it! (https://github.com/wobsoriano/lexical-vue)
As for the backend, I wrote a server that runs on Cloudflare Workers and Durable Objects. Super impressive products, btw.
One nit about the readme on the GitHub repo is that it's not immediately obvious how to pass state into/get state out of the component. Would be nice to have an example of that.