Google seems to have proactively moved Borders and Labels, along with Roads and Places to "Outdated". A move likely intended to eliminate duplicate work with maintaining the product alongside Google Maps. Hopefully it does not signal a slow decline in Google Earth's availability.
Your guess seems to be right.. Based on your suggestions you probably need something like this:
// PIXEL EXTRACT PROOF OF CONCEPT FOR COLLECTIONS:
var collection = ee.ImageCollection('LANDSAT/LC08/C01/T1_SR')
var outputData = ...
Google Earth does not have a tool for multi-selecting features geographically. To do that, you'll probably want to bring the KML into GIS software of some sort (like QGIS), where you can do all sorts of selections, by geography, attribute, distance, etc.
I can't find an answer to this online, so I figured I'd write what I found out since I was having the same problem. I received the same GE error and could not figure out why. When I was trying to create a Super Overlay, I also was streaming and had several Word docs and Excel sheets open. In other words, I was using a lot of services. I shut down Word ...