Why: Currently there is only an option to get the failed notifications with no ability to take actions over the API.
What: Resend failed notification. The resend can be 1 by 1, bulk of mentioned notifications by id or encoded key or all failed notifications of a specific type (Email/SMS/Webhooks)
Even from the UI you have to go one by one in order to resend. A bulk resend will be appropriate for UI usage as well.
How:Expose an API endpoint to resent failed notifications.
For the UI have a checkbox ReSend failed.