pandoc has infinitely many devices for including various commands. A lua filter - to take one standard example - can manage basically anything you cook up. The going AIs can write them for you and your triggering syntax at the drop of a hat. Inter alia, you can write your restructured text in markdown and include bits like this.

Here is normal Pandoc Markdown text.

```{=rst} .. note:: This is a native reStructuredText directive! Pandoc will not parse or change this text. It goes straight to the rST output writer. ```

Back to normal Markdown text.