Is it possible to create a treemap in Kibana? Treemap is not among the visualizations types shown in the visualize tap. Is there a plugin out there?
This enhancement request in GitHub seems to be what you're wanting added https://github.com/elastic/kibana/issues/11790. If you would please read that issue and make sure it covers the behavior you're wanting to see added, and then 
it, it'll help us prioritize.