mauri_murillo
Databricks Partner

This payload worked for me:

URL: https://{databricks_instance}/api/2.0/account/scim/v2/Groups/{group_id}

PATCH with this payload

{
"schemas": ["urn:ietf:params:scim:api:messages:2.0:PatchOp"],
  "Operations": [
{
"op": "add", 
"value": {
"members": [
{"value": "{user_id}"}
]
}
}
 ]
}