Make sure you are editing the ui_character_db.bin file that's inside your region's/language's data folder("data(us_en)", "data(us_fr)", etc.), otherwise, it won't show up in game. Also, make sure you are hitting return after every entry value you update, or the program won't save it.
I made the same mistake and couldn't figure it out for the life of me until I looked in my region's data folder and found an identical file.
On a semi-related note, I figured out what to edit in ui_stage_db.bin to make all the stages playable in 8-player smash.
You can't use the Parameter editor though, because it corrupts the file for some reason. You have to manually hex edit it.
Once I finish editing it so all regular and Omega stages can be played with 8 players, I'll upload it here and to gamebanana