It's really hard to know exactly what you are doing, but in general, any entity has attributes. In flat files, like text files, the attributes are usually different files. So in an role playing game you would have a file of characters, a file file for armor, a file for weapons, a file for treasure. Each file is tied to the main character file by some unique ID.
Without knowing the exact structure of your files, I can't really say what the relationships are or even if it is actually relational. I can't be much more help than this without actually doing it for you and I haven't the time.
If all you are doing is editing the files, why not just import them into a spread sheet and setup macros?
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