The new JSON Data option is available in the drop-down list of the Data Sources for most of the widgets. Use that option to provide static JSON data that is stored within the widget configuration and merged with dynamic data sources — useful for chart thresholds, label mappings, or fixed lookup data.
The toolbar above the editor allows you to undo, redo, format, or copy the current JSON content:
The new option is not available for widgets, like Calendar and Device Details widgets, that support just a fixed dataSource type by design.
For more information about the widgets types, refer to user guide.