How to Enable Edit Mode for Anonymous Users on Gamma API Presentation URLs

I have a question about one of the new features on the Gamma API. I have generated a presentation externalAccess set to edit. However, when I go to the URL in incognito mode, I only have view access. Is there a special URL format to send the anonymous user to the presentation in edit mode versus view mode? I looked through the docs, but did not find any additional info. Thanks!