In short - is there any sensible way to do it at the moment ? Or a workaround ?
With discovery - I can manually fix saved searches (under management) and get the results I need (otherwise I can't even do basic search for a nested field).
With visualizations though, it seems Kibana uses their own scheme of sorts when saving / exporting, so it doesn't seem I can do anything with it (unless it's documented somewhere and such functionality is supported).