Sub objects vega lite

[jen-huang]

Apologies for the late reply. Check out Yuri's suggestions in this thread:

Kibana vega viz plug-in:multiple aggregations: how-to?

@nielsen-at-cgt Vega-Lite does not have a good built-in handling of nested data results, so I would advise you use composite aggregation. See an example in the video linked from the recent Vega blog post. If you need to process nested data, you can use full Vega language instead - the "group" mark can be used to draw pre-faceted data.