Music file is not apearing as iMovie Music Library

I have a large file of music tracks on an external drive. I've followed the Apple article directions for changing the location of my Music Library (Music > Settings > Files > Change > select desired file). I picked the desired file on the extrernal drive and then restarted. I expect that within a half hour or so the music in the designated file would be accessible in iMovie. It isn't.

I've dragged tracks from the extrnal drive to iMovie videos, but it would be a little easier if this file showed up directly in iMovie.

Suggestions?