iMovie offers three ways to let you mark video footage so that you can find or sort it later. Marking video can speed the process of creating projects because it facilitates finding the exact footage you want.
Marking video as “favorite” or “rejected”: In most cases, your Events (source video) contain footage that you’d like to use in projects as well as footage you would never use in a project. You can flag clips in your source video as “favorite” or “rejected” as you skim the video. Later, when you’re creating a project, you can sort the Event browser to see just the video flagged as “favorite.”
Tagging video with keywords: Tagging your Events with keywords helps you keep your video library organized and makes it easier to find the specific footage you want. For example, you can tag all the landscape shots from your last vacation with the term “landscape,” and later, when you’re creating a project featuring your vacation, you can easily find all the landscape shots.
You can add any combination of keywords to any clip so that you can sort using very specific parameters. For example, in addition to tagging some of your video with the keyword “landscape,” you can also tag some of your shots with the additional keyword “trees” and others with the additional keyword “family.” That way, you can find footage featuring your family against the landscape, footage featuring trees, and so on. You tag video with keywords using the Keywords window.
Adding comment markers and chapter markers: You can mark any selection of video in your project with a comment and then easily return to it by choosing the comment marker from the markers pop-up menu. Comment markers are functional only in the Project browser.
You can also mark any frame of video in a project with a chapter marker and then easily return to the frame by choosing the chapter marker from the markers pop-up menu.