qmd is a common markdown format that can be used by R, python and Julia notebook users https://nbdev.fast.ai/tutorials/qmd_intro.html and is more friendly for version control that the standard ipynb format.

It is developed by Quarto - https://quarto.org/docs/get-started/hello/jupyter.html. It is already supported by jupytext so the addition might be as simple as recognizing the .qmd extension.