15- Edit as a new project
To make changes to a video that is done, you can either go to your video's page and select Edit as a new project in the top right menu "Options".
You can also do this on the page with all your projects and videos. Roll your mouse pointer over the video you want to edit, click the down pointing arrow that appears and choose Edit as a new project.
Doing this will not change the initial video, but will open a new video project in the editor using the first video as the starting point. If you produce another video, it won't delete or change the original video.