Editing retroarch.cfg

Please forgive me if this is a noob question but on my Shield TV I’m attempting to edit the retroarch.cfg file to swap the OK and CANCEL menu buttons. I’m using ES File Explorer Pro. Problem is, when I edit the file in ES Note Editor it only shows me the top half of the file. I can scroll all the way down and it just stops and won’t allow me to scroll further. Any ideas on how to get around this? Is there some sort of line count limitation with that editor?