I know that Notepad++ has been said a lot on here, and a big upside is its free. I personally use phpStorm, which is just a specialized version of JetBrains intelliJ. I highly recommend anyone look into their stuff, can’t recommend JetBrains products enough, I mean google used it to build their official Android Development Studio (which I also use). It handles multi file projects better that what I’ve seen N++ to be able to do, and it automatically detects new languages you haven’t opened before and downloads the plugins for them (it did it with .lua files for me.) I believe they have a version geared towards java (which json was originally created for) that is free IntelliJ IDEA: The Java IDE for Professional Developers by JetBrains , though I’m unsure if it’s free, or a free trial.
It might even be possible to use Android Development Studio which you can get for free, never tried to use it for anything other than android apps, but who knows.
That ends my rant.