A missing trackpad gesture
If you’ve performed an in-place upgrade, you might not even notice this change. However, if you’ve done a clean install or just bought a Mac, you might wonder why the three-finger drag gesture has disappeared from your Trackpad’s preferences pane. It hasn’t been removed from OS X altogether; Apple simply moved it to the Accessibility pane, despite it being yet another of those settings that is more broadly useful than that location suggests. In that pane, click Mouse & Trackpad, then Trackpad Options, turn on Enable Dragging and set it to ‘three finger drag’.