If you really understand programming, even Notepad or nano are good enough. (I do most of my programming in Edit Plus, because I bought it years ago, and I'm comfortable in it - I don't have to waste time looking for "how do I do ...?)
If not, I'd suggest staying with Android Studio. (JSON isn't programming, it's a data format. An Android editor has to be able to handle Java and Kotlin, which AS does.)