Or #4: You've got a custom view in place for a game that pares down the list significantly. You suddenly need to find a topic that's not in your custom view. Hit the invert button and that topic instantly appears in the nav pane on the left. Fast, easy, and no meaningful in-game interruption to find the info you need during play.
'Cause we all know that players NEVER choose to go left when all the neon signs from the story tell them to go right...
