I just found this online, and I thought it was really cool as a nicer representation of xml data in a compatible format (as I really don’t like xml’s format, particularly the closing tags):
https://innig.net/software/sweetxml/index.html
I hate XML like any sane and rational human being does, but I’m not sure this would be a good fit, given that we already have support for JSON (even if it does need to be fleshed out a bit more, like for material definitions and whatnot). If you really want to modify data files by hand, it’s probably better to go with a more conventional format such as JSON, than a niche format like that SweetXML.