Adding existing service to Swarm Mode overlay network

Is there support for adding an existing service to a Swarm Mode overlay network? There is no problem creating the overlay network and service via the 1.24 APIs, but the only mention of attaching to a network is at service creation time. My use case requires a service to be dynamically be added to a network after it has been started, but that behavior does not appear to be supported in the ‘service update’ API.