[anaphylactic]

I'm guessing XML doesn't count as a text-based file format? Otherwise, that's what every office suite (technically a zip file of XML files, but that's splitting hairs), vector editor, and graphical HTML editor already does.

Anyway, I especially like the `sc` spreadsheet format and editor as an example of a GUI tool that works with text-based file formats. Despite the giant disclaimer at the top of each file saying not to edit it, it's shockingly human-friendly.

[nerdponx]

XML is OK, but it's not exactly human-readable, nor does it play well with version control tools. You can actually edit OpenSCAD and Markdown files and be reasonably productive.