This feature has been deprecated, and will be removed in a future release of Appian.
You will no longer be able to send custom alerts from your process models to the Alerts tab in /designer. You can still find system alerts in the Alerts tab.
Use the Send E-Mail Smart Service to send messages to users or groups from a process.
For information about the Send Alert Smart Service [Deprecated], see the Appian 16.2 documentation.