How can I alter "FeatureType" of a Google Map

v4.9
Currently, I don’t see a way through the UI to do this to a Google Map.
I’d like to know how to add additional “custom” code to execute on a Map.

per this thread: https://developers.google.com/maps/documentation/javascript/style-reference

Simple JSON to further customize the appearance of a map.

This is the map I get with GoogleMaps now (cluttered):

image801×508 173 KB

This is the map I’d like (less cluttered):

image1011×633 120 KB

You can see how FeatureTypes are being shown/hid here:
http://jsfiddle.net/z2576smt/