Toggle switch for ReplayGain

[Thomas]

I use per-album RG when playing normally, but when I am playing a playlist with tracks from multiple albums, or shuffling the entire collection, a quick switch to move between ReplayGain modes would be advantageous, and save having to go into the preferences menu (and remember to set it back later!).

Sorry to bombard you with requests. I hope others will benefit for any potential implementation too.

[GoneMAD]

I can add a gesture action similar to toggle mono.. adding anything to the UI will have to wait until I overhaul the UI for 1.5