I do this: add the finished file to the audio video, right-click the video track on the timeline, click "Split the audio" in the pop-up drop-down list (so that the audio will not be deleted), then click the video track (note: if you click the audio track, the operation behind it will be audio), pull the "timeline" to the beginning of the picture you want to delete, cut it, and similarly, cut it to the end. After editing, recreate the video file and save it.