do you deliver a YAML editor with your software? Because people will use notepad or nano to edit that stuff.

Sort of, I deliver a GUI that exports into YAML for pretty much only reading, portability, and version control. People are expected to do the editing in the GUI, only using YAML for editing when doing complex regex operations that my GUI doesn't support.

If people aren't editing it by hand, why does the format matter? Why not just use JSON? Tools for too-complex-for-the-GUI manipulations are at least as good for JSON as they are for YAML, and the editing is less error-prone.

Internally it is JSON. It exports as YAML for readability when sharing on discord.