If you use Alfred, LaunchBar, QuickSilver or other similar products (and if you don't, you really should!), then you already know what this is all about. XCActionBar is at present only partially supported in Xcode 9. The vast majority of custom actions operate on text and therefore require access to Xcode's internal text views which have changed significantly in Xcode 9. I know of a few other plugins in a similar situation and people are hard at work trying to figure out what the new hook points are. I'm currently not in a position where I can dedicate a lot of time to research this, but I will definitely get to it at some point.