That’s a good question. I’m not aware of any user facing documentation in that regard. I think part of the idea is that the built-in tips and inline should help be the main resource (that and making things increasingly intuitive). Also Markdown itself is a de facto standard so there’s a lot of generic bits that carry over and aren’t necessarily NC specific.
That said, if you’re inclined to look at the the code a bit here are some resources. I have no experience with this area of NC’s codebase so hopefully I’m not leading you astray! With that caveat, it looks like most of the keyboard shortcuts are here:
And the modifier keys (different for each platform - i.e. PC vs. Mac) are here:
To extend/tweak the inline help or tool tips or any other adjustment like that, you’re also always welcome to submit a pull request (PR) to either the Text team with your changes. Or, similarly, to the Documentation team to extend the User Manual.
You can also search for and comment on relevant existing issues (or create a new one) within those respective repositories if there is an enhancement idea you feel strongly about, but aren’t able to implement yourself.