In order to remove all items from a collection, you must open up google chrome, firefox, opera, etc. and go to the page of your collection. Click on edit collection. Now right-click on the scrolling bar for subscribed items or whatever tab you added the items from. Click inspect element. Now at the bottom-right corner, there should be a box inside a box inside a box etc. Double-click on the second number in the thing that says "849 x 200" and change the value from 200 to 900 or higher. Now hit enter and click on Console. Copy this: javascript:(function(){jQuery('.itemChoice.inCollection .itemChoiceStatus').map(function(){this.click();location.reload(true)})})()

There ya go! removed!