In my experience all necessary ir codes were in the drop down lists. And they all worked as indicated. the names may have been a tad generic, but educated guessing would figure it out. I never had to learn a code.

I'd start from scrath again.
Make a picture of your replay modes, and the desired final button mappings. And start remapping. If memory serves I never had to re-map any of the the NAV & select keys, they were fine in their out-of-box respective menus 'Play Mode' & 'Mavigate Mode'