Content Patcher's ConfigSchema should not restrict players to a limited set of allowed values. Instead, make AllowedValues optional, allow Default to be any arbitrary value if AllowedValues has not been defined, and allow players to enter arbitrary strings. A use case for this is to allow players to set arbirary names to items in the generated config.json instead of needing to edit content.json directly.

Done in the upcoming Content Patcher 1.7. Thanks for the suggestion!