For each step, make sure only the "Manage files" of other editors do not contain files, or information from other editors Open a page where there are multiple blank editors Quiz settings for instance Open the Manage files plugin Make sure there are no files in there Add an image to one of the editors Make sure the image is in the manager when clicking on "Manage files" Switch to HTML and duplicate the <img> tag, but change the name of the file slithly Make sure the "Manage files" now displays the missing image Remove the real image from the editor Make sure the "Manage files" displays a list of "Unused files" Try harder to break things PS: The height of the iframe in the dialogue can be a little small, or not well fitted on small screens, this is a known problem