Filter Event Attendees / FilterEventAttendees (internally is.workflow.actions.filter.eventattendees)
usage
FilterEventAttendees 
arguments
source json (for developers)
{
	"ActionClass": "WFContentItemFilterAction",
	"AppIdentifier": "com.apple.mobilecal",
	"Category": "Calendar",
	"CreationDate": "2015-01-22T08:00:00.000Z",
	"Name": "Filter Event Attendees",
	"ShortName": "Filter Attendees",
	"Subcategory": "Event Attendees",
	"WFContentItemClass": "WFEKParticipantContentItem",
	"Parameters": []
}