The window sizing for the "Add Global Category" pop-up window is the same width as the rule window it covers.  If you do not click the "save" button and click on the rule window behind it, which is in view, it does not save your changes.  Would it be possible to increase the initial height of the "Add Global Category" window to be longer than the rules window so that it cannot accidentally be exited out of when trying to save it.  See image: