I know that this request has been archived. However, I would like to resubmit this request. Having an undo button adds to the ease of use and familiarity among programs/platforms. Ctrl-Z is an option, but not all users (including students) are familiar with this option. When you change the formatting on a page and you decide you don't like it, it would be nice to have a simple icon that can lead you to go back for a do-over.