I'd go with TOML for simple configurations. It has its flaws (numbers are doubles and multi-line strings are plantform dependent), but editing by hand is reasonable and it's not as complex as YAML.
I find it incredibly hard to understand anything in TOML that is more than simple, unnested key-value pairs. If you get into arrays, maps etc. then TOML is a nightmare to read.
I find TOML even worse. While it dodges some of YAML's issues, it can't decide if it's a super-INI file or another super-JSON. Also there is no way to format it to hint the human reader about the tree structure, making it un-navigatable.
