Custom events can be created as delivery method of a campaign. So that the push notification will be sent when the event is triggered.
To use this functionality, go to delivery method tab:
Fullfill the form, where "Event Code" is a required field. It must be the same code that is sent from the app/web, and optionally it can be set the range of dates where the campaign will be active, and the range of hours during the day where the custom event can be triggered.
When you are done, click on "Save and Enable"