I have to update the locator service url in dozens of AGO hosted web apps and can't seem to do that in the AGO Assistant tool. Any other solution? Can this be added to AGO Assistant?
Have you added the new locator to your the utility services of your ArcGIS Online organization?
How many apps need to be updated?
You can manually update the locator urls in the data portion of the web app JSON if you select the option to View an Item's JSON. Clicking the pencil (edit button) will allow you to do this. It's not supported, but maybe give it a try on a sample application to see if that will resolve your issue.
Retrieving data ...