In the entire index, there are 11 unknown values:
Config type, with 5: Codec config API, ConfigToolKit, Forge Config API Port, Fzzy Config, and QoMC
Features, with 2: Forge Config API Port and QoMC
Config format, with 3: Forge Config API Port, MidnightLib, and oωo
Config method, with 1: Forge Config API Port
Besides that, Forge Config API Port and YAML Config both don't have an example config.
Bonus fact: the config library with the most unknowns is Forge Config API Port, with all 4 listed above.