You can manually add or delete scenes once you are in the storyboard.
To add a new scene follow these simple steps:
Navigate to the particular scene before or after which you want to add the new scene. For eg, scene 5 in the below screenshot.
The Plus signs that you see to the left and right of the scene visual, are the buttons to add new scene before or after a particular scene.
Blank scene, as the name suggests will add a scene without any text or visual. You can later add content as per your requirements.
Text only will add a scene with a blank text box for you to add the text content.
Visual only, will add a scene with an option for you to select visual that you want for that scene
Text & Visuals, will add a scene and give you option to add text and will automatically add a visual which is relevant to the text that you added.
Linked scene, will add a scene that has the same visual as the scene you are linking this new scene with and you will get a blank text box to add text.
To delete any scene, you can see a Delete Button right below each scene, click delete and that scene will be deleted from your video.