I haven't found a markup language that I really prefer for configuration files, but JSON has been reasonably nice to me in NPM configurations and VS Code settings and I haven't ran into problems yet. I understand the motivation for TOML but it has the same ambiguity problems that YAML does. There's something to be said for not being too flexible, or it'll fall into the same trap as AppleScript did. Humans might prefer the convenience of ultra-flexibility at first, but sooner or later our intuition will just not match up with the actual rules, and we'll have to spend longer than we wanted to looking up arcane syntax documentation. That's been my experience with YAML anyway, like every single time.