When I click the “Install add-on from disk” button, a Finder/file chooser window is opened. However, zip files are greyed out. If I unzip a zipped add-on (for instance, the ports add-on), I can open it, but that just navigates one directory deeper; it doesn’t let me install the add-on.
Am I missing something? Do I need to do something else to install an add-on from disk?