Turn down audio in a time range
Please shamelessly steal that FCPX feature where you can turn down audio in a certain time range and it will automatically make/modify the keyframes.
I often want to turn down music under dialog so that's four keyframes to make. It would be nice to be able to select the time range I want to affect and then turn down the volume there just by dragging down the volume or using the volume modifier keys.
Jim Simon commented
There is a new Auto Ducking feature in 12.1.1. Try it out.