Apply Normalize Region/Cell Gain Again    ⌃G

I habitually change Region gain on tracks that I mix. My current target is peaks of -12 dB. I don’t change region gain if all of the tracks come from a “live” performance where players are typically self-adjusting. In those cases I work with the faders all set to about -9 dB to start.

Normalize audio regions in the Tracks area — Apple Support

You can normalize the gain of selected regions in the Tracks area, without opening the regions in the Audio Track Editor. The Normalize Region Gain menu command is non-destructive: the original file isn’t altered, so you can return it to its original state.