I'm a bit of an idiot that I just figured this out...
When you are in Browser mode and turn the browse knob, you get the 2-column list of rigs. This way seems initially a quicker way to jump around rigs. I found I could get around quicker turning the browse knob vs. clicking the Rig right/left buttons. Also, turning off auto-load makes things a bit faster but going from A-Z can take a while (esp when you're like me and haven't deleted your unused factory rigs yet).
What I didn't realize (and this is kind of embarrassing it took this long to figure this out...), but when you are in Browser mode but have NOT used the browse knob to enter the 2-column window (so you're just looking at the current rig name), using the Rig Up/Down buttons navigate by the first character of the rig name. So going from A-Z now takes 26 clicks. So I can get from my first to last rig in about 2 seconds. Yay
This is probably pretty obvious to most but somehow eluded me. Hope this helps someone!