JSON - Load Subset of Files Based on Key in File

Okay, I'm trying to learn how to use JSON. One thing I want to do is allow the user to select one of a number of subsets of options. Imagine how Bioware separates out their saves of different "characters."

Basically, when the user saves a set of parameters, have part of the JSON file record a certain value the user picks (say 1, 2, 3, 4). Then, when loading a file, check against this value (say, 3) and only show JSON files with that certain value.

More detailed idea of what I'm working with here. Basically, a CA has neighbor effects, and the user should be able to load a file with parameters, but only from a certain type of neighbor effects (and number of cell types, but that is just more of the same problem).