Note: The system re-caches the template by default every 24 hours.  To change this to a shorter time, find the Manage Administrator Profile Values setup task in Setup and Maintenance, and change the BIP_CLIENT_REFRESH_TIME profile to 15 minutes for testing new templates.  Just remember to return it to 1440 (24 hours) once testing is completed.

If the BIP_CLIENT_REFRESH_TIME profile isn't on your system, you will need to create it.  To do so, following the instructions here: https://docs.oracle.com/en/cloud/saas/applications-common/22d/facia/apply-changes-to-workflow-notifications-soon-after-upload.html#s20072794