This is a follow-up to one of the possible answers to the recently-announced changes to the editor.
Prosemirror-math is a math editing framework that allows for direct editing of a rich-text preview. The mathematics is automatically rendered, and it is converted into LaTeX source when it is selected.
(One of the aspects that came up last time is that the default back-end is not MathJax but KaTeX. This will apparently be expanded in future, so the two decisions will become decoupled.)
Anyways, the new development is that a working demonstration version of this editor is now available, which is now ready to play around with. So $-$ what do you guys think? Is it usable? Does it work to produce complex answers?