I'm basically wondering how I can perform this operation in Kibana:
https://www.elastic.co/guide/en/elasticsearch/guide/2.x/_dealing_with_null_values.html#_missing_query
You can add a new filter and then customise that with whatever query you want in it.
See https://www.elastic.co/guide/en/kibana/current/discover.html#discover-filters for how to get started
Ohh, great, @warkolm I knew you could add filters but never realized you could edit them inline like that in Kibana. Thanks!