Announcing: Work has started on CodeMirror 6

No, still not stable, or even documented, at all. I recommend waiting.

One feature I like is being able to highlight text - however I hate how you have to use Ctrl commands or inserting @h@ to highlight rows. I would like to mark lines like you do in Visual studio where you click on the numbered row and it highlights on the fly

There’s now documentation, and an npm package. There’s still features missing and bugs, and things will no doubt continue to change in breaking ways, but going forward those will be documented in the change log.