There is an endpoint to add external outbound calls to conversations. https://marketplace.gohighlevel.com/docs/ghl/conversations/add-an-outbound-message.
Would be great to extend this to outbound messages so we can add messages from custom providers that have been sent via workflows and other means.
Seems like the endpoint would only require a new message type (sms, custom etc...) and text for the message and everything else is in place.