Apple Gives You 15 Trackpad Gestures. Here's How to Add Your Own.

macOS ships with roughly 15 built-in trackpad gestures — and no way to add more. There is no public API for custom trackpad gestures. To get gestures Apple didn't ship, you need a third-party app, and your options split by input device: BetterTouchTool for the trackpad, mouse-gesture apps like…