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In the readme, it says your saved games are stored in ~/Library/Preferences/League of Legends Preferences/. I opened every single file in that location, and none of them contain game preferences (keybindings, video/audio settings, etc), unless I'm missing something. I also inspected all files inside the LoL application bundle package, and performed systemwide searches on various keywords, but I couldn't find anything.
I was looking for a file much like the pc version (LoL/game/DATA/CFG/game.cfg, input.ini), where you can edit your keybindings via a text file.
I accidentally screwed up my initial mac keybindings, and was unable to easily fix them by editing the file directly as I would on the pc.