put https://app.asana.com/api/1.0/custom_fields/
A specific, existing custom field can be updated by making a PUT request on the URL for that custom field. Only the fields provided in the data block will be updated; any unspecified fields will remain unchanged
When using this method, it is best to specify only those fields you wish to change, or else you may overwrite changes made by another user since you last retrieved the custom field.
A custom field’s type cannot be updated.
An enum custom field’s enum_options cannot be updated with this endpoint. Instead see “Work With Enum Options” for information on how to update enum_options.
Locked custom fields can only be updated by the user who locked the field.
Returns the complete updated custom field record.