To mark video that features camera pans:
You can have iMovie mark the sections of video in an Event where the camera pans left or right. You can then filter for these sections, which can be useful when creating projects. The sequence you’re editing may require a pan from left to right or right to left, for example, for continuity and pacing of the action.
In the Event browser, select one or more video clips that have already been analyzed for stabilization.
Choose File > Analyze Video > Mark Camera Pans.
The File menu appears in a light gray bar across the top of your computer screen.
If the video hasn’t already been analyzed for stabilization, choosing this option starts the stabilization process. After stabilization is complete, iMovie marks the sections of video that contain camera pans.
Video that has camera pans is marked with a blue line across the top.