Clean code is one thing, but keeping your localizable files clean is another. If you have any of these issues:
Five major problems that commonly occur with localizable files are unreadability, key duplications, mismatched keys across different string files, missing keys but are being used in code, and extra keys not used in code
you should be checking out this post from Gino on how to get organized.
How to keep your iOS localizable files clean — Swift script edition by Gino Wu