How to set a multiple alert/reminder for the same calendar event?

Using Calendar.app I can add an event and then add an alert to it, and set when the alert should be. But I only seem to be able to add one alert per event.

How can I give myself a repeating reminder of an upcoming event?

Have a look at: Set event alerts and receive notifications in Calendar on Mac

Particularly step 3.

Set an alert for an event

1. In the Calendar app on your Mac, double-click or force click an event to view event details, then click the event’s time.
2. Click the Alert pop-up menu, then do one of the following:

• Choose a time or day.
• Choose Time to Leave. This option only applies if you added a location. For information about how time to leave is calculated, see Add a location.
• Choose Custom, then choose an option:
  • Message with sound: Displays a notification on the screen and makes a sound.
  • Email: Sends you an email.
  • Open file: Opens the file you choose.

3. To add another alert, place the pointer over the Alert pop-up menu, then click the Add button.

        You can set only one alert for Exchange events.

To remove an alert, click the Alert menu, then choose None.