Hello Alicia,
Thank you for submitting this suggestion! I can definitely see why a "Not Participated In" user filter for initiatives would be helpful for engaging and targeting users who haven't registered yet for a volunteer need/opportunity that is part of an initiative. I'll be adding this suggestion to our enhancement board and bringing it up in the next meeting.
Once again, thank you, and wishing you a great week!
Best,
Annette
Alicia Monroe
Adding the option of NOT PARTICIPATED IN would be appreciated as it would allow the option to email those who may not have registered for an opportunity through an initiative instead of emailing everyone on the list regardless if they have registered or not. Sometimes targeting those who have not registered is a way to get them engaged and signed up.