Currently, the only way to stop the charges for the AIDP Workbench is to delete the instance. It is not possible to pause the service as it is with other OCI services.
It would be really useful, especially for development instances, to be able to pause the workbench when not in use to avoid incurring charges when there is no workload being placed on the system and means customers can retain already built content can be retaind without having to take backups.