Edpuzzle aggressively reverts the playbackRate of a <video> element, so you can't simply change it to increase the speed. Thus, a more aggressive response is necessary to combat it.
Firstly, we get the <video> element:
video = document.querySelector('video')Then, we get the setter function for the playbackRate property using Object.getOwnPropertyDescriptor(HTMLMediaElement.prototype, 'playbackRate').set. It is called with the <video> element as this and with speed as the new value. This way, the <video> element is properly notified of the speed change by simulating assigning a value to playBackRate directly (ie using =).