Anyone curious about how keyword collections work in FCPX (and the basis for the Feature I'm so adamantly requesting for PP), here's another video that explains it: https://www.youtube.com/watch?v=m5m0DNR4HUQ.
It might not be the best produced video, but it's the one I found where the reviewer gets to the point the quickest. A quick search in YouTube for "fcpx keywords" will bring up a lot of results. Happy findings!