Instead of folders (like everyone seem to ask in every thread like this) a custom tagging system would be better (since a deck could belong to multiple categories), but I'm guessing that'd be seen as too "fiddly" for the average user so I'm not holding my breath :)
What I think could be feasible though is a compact mode? Like how in the deckbuilder you have the option to choose between two card sizes, one big and one smaller, it would help if we could have sth like a list view in the Decks window. The boxes look very pretty, but gets hard to scroll and browse through when you have too many.
Even if none of these are doable, can you guys at least make the format dropdown menus full-height so we can see them all at once? The three-lines view is so unnecessarily hard to use. It reminds me of web sites from the 90s.