Shotcut is a bit of a throwback video editor, but it’s free, has features iMovie does not. Jack Miller:
Video editing features standard 3-point editing, external monitoring, plenty of cross-fade transitions for both video and audio (and a bunch of video wipe transitions). Audio can be mixed across all tracks in the timeline, and Shotcut handles video compositing across all tracks, too… What about audio? Shotcut handles more than what you get in iMovie, including mixing across all tracks, cross-fade options, and a bunch of useful filters from balance, bass and treble, delay, expander, gain, compressor, limiter, high and low pass, normalize, and much more.
Very impressive for free.