Re: How do you make a calendar event repeat every year?
SOLVED
For anyone looking to create a repeating event, like a birthday or anniversary, or holiday, I've found a solution that's working for me.
I was able to create an event using Create O365 Group Event. I then went to the calendar and manually set that event to repeat every year. Using Graph API, I could find this event and see the relevant values needed to make it repeat: "recurrence" and "range".
Using the O365 Group Send HTTP Request action, I could PATCH the event with these desired values.

{
"recurrence": {
"pattern": {
"type": "absoluteYearly",
"interval": 1,
"month": "@{outputs('ComposeMonth')}",
"dayOfMonth": "@{outputs('ComposeDay')}",
"firstDayOfWeek": "sunday",
"index": "first"
},
"range": {
"type": "noEnd",
"startDate": "@{triggerBody()?['text']}",
"endDate": "0001-01-01",
"recurrenceTimeZone": "Eastern Standard Time",
"numberOfOccurrences": 0
}
}
}