Unfortunately, TW isn’t really (1) optimized (2) for working with nested JSON structures. Personally, I’d love to see a core modification to $action-setfield like the one @EricShulman suggested here (or even a new $action-setjson widget, as @jeremyruston suggested last time I brought this up). This would presumably let us use the missing-$value trick to delete an index, in addition to making it generally easier to set JSON index values. But in the meantime, I have to recommend you try to avoid complex JSON objects if at all possible. 