You may find necessary to be able to manage an ARS instance remotely from another ARS instance, that is on a separate environment.
For example: Domain A has ARS installed and configured and Domain B also has ARS installed and configured. You would like ARS B to connect and manage ARS A (remotely) and have them both displayed in the console, instead of adding domain A as a managed domain to ARS B.
Currently such feature is not available in ARS. An enhancement request (TF00448039) has been created detailing the feature.
The product team will evaluate the request and this feature may become available on a future release of the product.