Thank you for reaching out to us through the Community. At this time, we do not have the ability to add the registrants to a list from the management page of your registrants. I do apologize for any inconvenience this may cause. As a workaround, you can export the export the Event Report and import the Excel file into the necessary contact list. To export an event report:
On this page, you can customize and export the necessary information about your attendees that you require. For more information on this, please click here. With that being said, I have submitted a request in to our developers in hopes that this feature can be implanted within the product in the near future. Let us know if you need assistance with anything else.