There are two useful features I've found to be rare among markdown editors:

1) Inline application of markup. Discord does this for example. If you write text like this, the message preview retains the '*'s, but the text inside is italisized.

2) Persistence of text formatting when pasting from rich text. Roam Research does this. If I'm copying-and-pasting some rich text with e.g. a link in it, the link will be converted to the markdown format and then pasted.

I think to have a truly great markdown editor you need both of these things, but I've never seen an open source one with support for both. I've had a mind to find one and implement them myself, I might try that with tail.writer.

Discord's input is built on-top of Slate.js [1], which is sort of a more React-based alternative to ProseMirror. I've thought about building the same functionality on ProseMirror but I've always thought, inline decorations only work when you have a small number of marks. For example, you could have `~~==b==~~` be valid markdown, but not nice to look at.

[1] https://www.slatejs.org/examples/markdown-preview

Something like SimpleMDE ( https://simplemde.com/ ) ?

EasyMDE is the active fork.

https://github.com/Ionaru/easy-markdown-editor

Visual studio code does #1 for me if I'm editing a file with a .md extension.

I don't think it's plugin related, but if it is it'd be one of the top search results.