I use ctl-x frequently. Please don't eliminate it!
As far as quickly navigating to a given folder, the folder window automatically has this built in, doesn't it? If I have 4000 folders and only one of them starts with a "z", if I type a "z" while in the folder window, the focus immediately moves to that one folder.
It works on multiple characters, too, so if I want to move to the "music" folder, I start typing the word "music" and the focus will be moved to the "music" folder long before I've finished the word.
But, while we are in the process of asking for improvements..... the folder search function seems to ignore anything other than regular characters. Spaces, exclamation points, and other valid characters within the name of the folder don't seem to cause the focus to shift. Of course, I could just be a few versions behind (I'm still on 3.12c), but I'd upgrade in a second if folder search allows non-regular characters.