An inserted video is shown as a large '?' on both editing and in preview mode. It would be useful if this could be supplemented with the filename of the video, particularly when presenting to an external display, where it is extremely useful to know what the next item will be. For linked videos this must be available to Impress anyway - for embedded ones it would be useful to keep this to assist with navigation.
That would be a good improvement. Thank you for posting this.