I lost you there. Not that I'm criticizing you since I've gone the same route and built a complex UI tool to manage said config (complete with XSD schema validation and config schema migration using XSLT for version upgrades).
But now I realize that modern developers don't want a GUI to manage their config. We want to store it git, review changes and perhaps even write our own automation and templating around it.
YAML is certainly a flawed format for most of these purposes, but so is XML. It is unnecessarily verbose and it carries a lot of complexity which was designed for a highly-extensible generic document format, but not for configuration files. XSD, Namespaces, Entities, Embedded DTD, CDATA blocks... You can't just ignore all of these, and there are very few parsers out there which work on a well-defined subset of XML. And even there, the whole attribute-vs-child-element choice is a giant distraction and constant source for unnecessary bikeshedding.
YAML has serious ambiguity issues, but there are better alternatives that have great library support like TOML. We don't have to go back to the excesses of the early 2000s and use XML as a configuration format.