H i @cousens,
Sending of custom strings are not included in the current version of the plugin at the moment however will add this to the plugin dev roadmap.
You would need to make use of the GET SUBSCRIPTION and UPDATE SUBSCRIPTION actions and send through the subscription token of the specific RG record. So the subscription token would need to be stored and submitted in the UPDATE SUBSCRIPTION action. Unfortunately I wouldn’t be able to provide any additional support for this as it falls outside the scope of the plugin support.
Regards,
Pieter