You can control the appearance of clips in the browser by changing clip size, showing or hiding audio waveforms, and adjusting the duration represented by each clip thumbnail. You can also show information about a clip.
To change the appearance of clips in the timeline, see Change project settings in iMovie on Mac.
In the iMovie app 
on your Mac, click the Thumbnail Appearance button 
in the browser.
Drag the Clip Size slider left to decrease the size of clips, or right to increase the size.
You can display audio waveforms in clips in the browser. Waveforms display changes in the audio levels over time.
In the iMovie app on your Mac, click the Thumbnail Appearance button in the browser.
Select the Show Waveforms checkbox.
In the browser, you can control how much time is represented by each thumbnail in a clip’s filmstrip. If you have a lot of clips, you may want to increase the duration represented by each thumbnail.
In the iMovie app on your Mac, click the Thumbnail Appearance button in the browser.
Drag the Zoom slider left to shorten the duration represented by each thumbnail, or right to increase the duration.
Note: By default, the Zoom level is set to All, so that individual clips are represented by a single thumbnail each.
In the iMovie app on your Mac, click a clip in the timeline or the browser.
In the adjustments bar, click the Clip Information button 
.
Information about the clip appears above the viewer (from left to right):
If you selected a clip in the timeline: iMovie displays the clip name, the date and time stamp, how much of the clip is used, and the total duration of the clip.
If you selected a clip in the browser: iMovie displays the clip name, the date and time stamp, the duration of the clip, and the sharing history of the clip.