Jupytext docs > The percent format: https://github.com/mwouts/jupytext/blob/main/docs/formats-sc... :

  # %% [markdown]
  # Another Markdown cell

  # %%
  # This is a code cell
  class A():
      def one():
          return 1


  # %% Optional title [cell type] key="value"

MyST Markdown has: https://mystmd.org/guide/notebooks-with-markdown :

  ```{code-cell} LANGUAGE
  :key: value

  CODE TO BE EXECUTED
  ```

And :

  ---
  kernelspec:
    name: javascript
    display_name: JavaScript
  ---

  # Another markdown cell

  ```{code-cell} javascript
  // This is a code cell
  console.log("hello javascript kernel");
  ```

But also does not store the outputs in the markdown.