How to change the value of a user field through Restfull?
Assuming the user rest resource is enabled and PATCH requests are configured, also that the requesting user is authenticated to update the user, then:
send a PATCH request to: https://example.com/user/$uid?_format=json
Where $uid is the user id to update (e.g 12)
The request body should look something like this (json format):
{ &quot;field_motherid&quot;:
  [
    {&quot;value&quot;: &quot;new_value&quot;}
  ]
}