The Media Browser in macOS’s Open dialog was a powerful addition many years ago. You may not even know it’s called that: it’s the area in the left-hand sidebar in any Open dialog below the Media label. For most people, it will show Music, Photos, and Movies. Clicking any of those items will access libraries created or managed by GarageBand, iTunes, iMovie, iPhoto, Logic, Photos, Photo Booth, and others.
But Media Browser can be fickle. In May 2017, I wrote a column on how to disable the feature, because I’d tracked a system slowdown’s cause to the Media Browser’s underlying plug-ins—a problem some other users had seen at the time. Apple apparently fixed the problem or my Mac silently repaired itself, as Media Browser works fine for me now.
