Mikal getting a good little plug there for our Twitch channel, thanks! Though I'm not 100% sure the stream yesterday will quite cover what you're looking for in terms of JSON — purely because I'm still learning to use it myself.
That being said, I am planning on writing a tutorial about JSON-based dialogue systems, as well as using arrays for displaying text. If I remember rightly, there should be a shorter video stored on Twitch covering the Array method, and the full stream from yesterday will be up there for the next 13 days (and heading to YouTube soon!)
I could probably share the test file I've been using to build the JSON system if you like, and this video tutorial from Vimlark also explains the array system better than I probably do!
I have also used Dialogue Designer, and while it's a really neat tool, the exported JSON file terrified me 😅