[stephenwithav]

Run this on your Watch Later page in your console:

let x = $x;

let buttons = $$('div#contents div#contents div#menu button');

let delay = 1000;

for (let i = 0; i < buttons.length; i++) {

  setTimeout(() => buttons[i].click(), 100+(i*delay));

  setTimeout(() => x("//span[contains(text(), 'Remove')]")[0].click(), 800+(i*delay));

};

...increase delay if needed.