Turn on the Three-Finger Drag Gesture in El Capitan in Accessibility Options
The three-finger gesture that allows you to drag windows without clicking has been in OS X for a while, but in both Yosemite and El Capitan, the setting to enable it has been moved. It’s all over now in the accessibility options.
Open System Preferences> Accessibility> Mouse & Trackpad. Then click Trackpad Options, click Allow Drag and Drop, then select Three Finger Drag. Once enabled, you can move the window by simply placing three fingers on the trackpad and dragging. It’s a small change, but if you missed this option after an upgrade, it’s now easy to re-enable it. Of course, if you really want to customize how this gesture works, MagicPrefs or BetterTouchTool are still your best options.
How to enable the three-finger drag gesture on Mac trackpads in OS X | OS X Daily