This is a cool idea - I'm not sure where the best place would be to implement this, since we'd be bottlenecked on how Sphinx itself handles cross-refs (I think that you must put a label just before a header title, for example). But would be cool to experiment with and implement.

Oh its already in my thinking for myst-nb: I've already implemented a similar thing previously for ipypublish: https://ipypublish.readthedocs.io/en/latest/code_cells.html#plots-with-matplotlib

Nice - shall we move this to myst-nb then?

Yep sounds good 👍

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Anchors for cell based on cell IDs have been implemented in JupyterLab (jupyterlab/jupyterlab#13285) and nbconvert (jupyter/nbconvert#1897). There is also a related issue open on Jupyter Book repo jupyter-book/jupyter-book#1812.

Could the myst_parser expose the _heading_slugs logic from executablebooks/MyST-Parser#718 so that we could add anchors to cells reusing the same reference collection logic?

Edit: I mean having a function similar to existing generate_heading_target, but allowing to set an arbitrary slug (and use it on cell nodes).

@chrisjsewell would you agree that the above proposal of exposing _heading_slugs logic is going in the right direction? I can open a PR against MyST-parser to complement the preliminary work in #519 but would appreciate an early feedback.

#519 is ready for review; I will need help over there - despite many attempts the slugs do not get embedded as identifiers in the cells. It seems like the target processing code does not get invoked but I cannot narrow it down why.