I'm torn on this myself.
I have around 40-60 decks in my comp. (yeah, yeah, I know...)
I like being able to see more than 2 letters on the Deck selection tab, But I also hate scrolling.
Maybe having a toggle option in the preferences could be cool, so the app is flexible for everyone's different needs?
I trick I found, is putting your mouse over the decks and using the mouse wheel to quickly scroll (and by quickly, I mean 15-20 at a time).
If we're handing out options here, I personally would like the option to have the left and right arrow scroll the next segments of decks into view, Example:
Only showing 10-15 decks at a time, with a healthy name length visible on them, then click on the right arrow which now scrolls decks 11-20 (or 16-30) into view.
Honestly with a mouse wheel, I can navigate it pretty quickly and happily now as it is, but I know it's "different strokes for different folks"