A repeat with allowAdds with a nested repeat with images enabled with allowUpdates will allow a user to collect a new record and submit. It will then allow new images to be collected from the Inbox in the nested image repeat (shows blank as expected for images already taken) but the RowID of the repeat changes dropping the images taken with Collect.
I have attached the survey. Notice how the 'Collect' images get dropped when the RowID changes to accommodate the new image. Should this be allowed yet as it doesn't work.
With the 3.13 release of ArcGIS Survey123 we have added support for viewing existing images in the inbox. At the moment you can only view and add new images. In the future we are hoping to add support for deleting and updating images from the inbox.