The ArcGIS Experience Builder applications using custom widgets break when the custom widget is removed from ArcGIS Portal.

Workaround

1. Add the widget back to the Portal. Refer to this link: https://doc.arcgis.com/en/experience-builder/11.0/configure-widgets/add-custom-widgets.htm for more information.
2. Access the config.json for the experience via https://<PORTAL>/sharing/rest/content/items/[itemId]/resources/config/config.json.
3. Copy this JSON output to a .json file locally on your machine.
   1. Name this file config.json.
4. Search the config.json file for the old widget itemID.
5. Replace that old widget itemID with the new widget itemID.
6. Visit the updateResource endpoint on the experience(s) impacted by this problem. For example: https://<PORTAL>/sharing/rest/content/users/[userName]/items/[itemID]/updateResources. Refer to this link: https://developers.arcgis.com/rest/users-groups-and-items/update-resources/#json-response-syntax for more information.
7. Within this operation pass the following parameters:
   1. File: the config.json on your machine
   2. Resource prefix: config
   3. File Name: config.json
8. Once populated, press the Update Resource button.
9. This will upload the config.json with the new itemID for the new widget and will fix the application impacted.
10. Repeat this process for all experiences that are impacted by the old custom widget.

Steps to Reproduce