When you create a base view from a JSON data source, it exports the entire dataset. To create a view from a specific key, you need to create a derived view by right clicking on the base view and then New -> Selection where you can then choose your desired fields. Derived views let you delete any columns that you don’t want.
For more info you can refer to [Creating Selection Views](https://community.denodo.com/docs/html/browse/7.0/vdp/administration/creating_derived_views/creating_selection_views/creating_selection_views) document.
Hope this helps!