Google Duo is going to be adding a Re-Record feature and something called Drishti mode in an upcoming update to the video calling application. Right now there is no indication of when these new features might be added as the details surrounding their presence within the app, comes from strings of code that had been found within the APK of the latest version of Duo, which at this point is Google Duo version 23. Since none of the new features that were discovered are actually available yet it is possible that they could show up in version 24 whenever Google releases it.
While Duo is primarily an app meant for people to use for video calls, Google had implement the use of voice calls from within the app and just as voice calling needs to have voice mail options for users to leave messages for the recipients they're trying to reach, Duo's video calling functionality is seemingly getting something very similar. This appears to be what the Re-Record feature is going to be linked to. Video mail messages were discovered as an upcoming feature in an earlier version of the app and the re-record option it seems like will be a way for users to redo the video mail message if they accidentally mess up or simply want to add some more footage to it. This will also be alongside the option to back out of the message if they end up deciding they don't want to send it.
As for the Drishti mode that was mentioned above this appears to be a new camera effect mode that will have something to do with focusing on subjects in the video call, with an option to set things to automatically focus in on subjects, likely the faces of people in the call whether it be one or more people, this way it highlights the person in the call that you're talking to instead of everything in the room. There is also a manual focus mode mentioned and an option for "none" which is likely a setting for not having Drishti mode enabled at all. Lastly, it also looks like Google removed a few things from Duo, with these things being exposure compensation, white balance, and color effects from the camera.