For each metadata object the DELETE works. For updating the object use the PUT where the body will be response to the same resource from GET request that you can easily edit and send back using PUT to the same resource. So the workflow will be:
GET
metadata object- Update the object body (JSON)
PUT
it back on the same resource from which you got it
This works for all metadata objects. You can easily recognised those objects by
/obj/OBJECT-ID
Thanks for the question!