You can now edit specific Metafields on existing Objects via the API. The following API method allows you to edit specific Metafields identified by
key, without affecting other Metafields as well as add new Metafields. View in the docs.
The endpoint is:
slug (String) metafields (Array)
The Cosmic NPM module is also updated (3.2.19) to allow for this capability with the new method: