[jxy]

For equations and flowcharts, I would argue that the rendering is more important than the textual "code", so a "preview block" with rendered output would be very useful already.

A much better UI would be something like what you described, such as

- https://github.com/benrbray/prosemirror-math?tab=readme-ov-f...

- https://support.typora.io/Math/#inline-math