How do you use the Assistant?

Yes, that is possible.
It’s not really documented anywhere, but you need to call QueueMessage with a payload of

{
    command: "invoke",
    workflowid: "1234",
    data: {"arg1": "hello world"}
}

and send it to the queue of the robot ( the _id of the user the robot is running as or a role the user is a member of, that also has the RPA role checked )