Hi Mike
I'm quite inexperienced when it comes to JMS so I don't fully understand what a durable subscription is, I based my knowledge on:-
Open Messaging: Durable messages and persistent subscriptions
However I have had a look around the API Management support system and have found a similar request. It was suggested that the customer set the clientID under additional properties on the JNDI tab, which enable the durable subscription to be set. Unfortunately solution was never confirmed so I'm unsure if this will work for you or not. If not please raise request as an idea on this community and product management teams can review it for a future release.
Regards
Christopher Clark
CA Support