You can change the type of a scene only on the 'Storyboard' screen.
Step 1: From the drop-down menu, select 'Story' to change a 'Quote' or 'Question' scene.
Step 2: Click 'Yes.'
Make sure you decide all the scene types before you move on to the advanced editing stage; otherwise, you will lose those changes.
Here is a short video to take you through the process