To be quite honest I dislike using XML for human editable configuration files. Variations on Microsoft's .ini files (such as TOML) seem to work best for that, IMHO.
We use .ini files for all of our settings in our products, and they work great most of the time. The only weirdness creeps in when you try to store things with embedded CRLFs and need to escape/unescape them (not a big deal), and storing lists of things is a little difficult.
JSON is great in terms of flexibility, but .INI files are really easy to read because everything is on the left side of the screen/window at all times.
