I used json for creating procedural systems. There is one problem with files like json: they are not packaged by default into game files, you need to watch it yourself. Yes it is possible, not hard, but it is your responsibility.
Data Tables are nice, however have you seen Data Assets?
You can make data asset loader/manager, that scans certain folders for data asset of a type/class.
Then you can make folder structure corresponding to quests/story chapters. You put your data asset in those folders (that have some certain filename+folder naming convention).
Add to this blueprintable editor tool to see and modify them. And on top of it all you have tree structure (from file folder system), you can modify story just by moving Data asset file.
And you can also create editor tool that reads json and creates all data assets in correct folders.