You can now remove EnumValues from an EnumType FieldDefinition, and LocalizedEnumValues from a LocalizedEnumType FieldDefinition, on a Type. This feature is available in public beta.

These update actions are always allowed, even if the FieldDefinition is required and even if a resource still has a Custom Field value referencing one of the removed keys. Existing Custom Field values are not updated or removed, and are returned unchanged until they are explicitly updated. A later update to one Custom Field on such a resource can fail because the update revalidates all Custom Field values on the resource.