I am not aware of one, but if you're setting all tracks to the same value, you're not actually making a difference for yourself. You would see no difference if you had them all at 0.0 dB. Bumping it up would be done for specific, especially quiet tracks.
Thanks CritterMan. I understand that there is no difference when considering MusicBee in isolation, but relative to other playback devices, it does make a difference.
The reason I set this higher, is to reduce the difference in perceived loudness when playing something through MusicBee vs., for example, Firefox -> YouTube. Windows doesn't allow me to boost the volume for a particular application, only reduce the volume. MusicBee is always the quietest.
The other scenario/reason is that normalised tracks (at 0.0 dB) played in my car stereo vs. radio playback at the same in-car volume level, produce a much quieter perceived loudness for the normalised tracks. The original unnormalised tracks sound much closer to the radio volume. This is also true for all of the other playback devices I've tried.
By setting it to an offset of 2.0 dB it brings it closer to the other
standard volumes.