So, I use the subway to track when different fields enter or stop being present in stories, by when they first enter via an event, or when they stop continuing after an event.
Now, to make it easier to see, especially with many more fields/things that can be tracked, to have a subway line be highlighted, while the rest becomes soft of faded out. Meaning, if i hover my mouse over a track, only that track would be fully visibile, while others are faded out.