For a limited time, installing a directory hierarchy to the old GNOME/KDE specific locations such as /usr/share/applnk and /usr/share/gnome/apps will continue to work as way to add your application to the menu system as well. There are two ways to support both the old and new menu systems at the same time:
              If you add a Categories line to the desktop
              entries in the legacy hierarchy, implementations of this
              specification will ignore their location in the legacy hierarchy,
              and arrange them according to Categories instead.
              This allows you to install a single desktop file that works in all
              cases, though on the down side it's in a legacy location.
            
              If you add the line OnlyShowIn=Old; to a desktop
              entry, then old legacy implementations that ignore
              OnlyShowIn will still show the desktop entry, but
              implementations of this specification will not. Thus you can 
              add an "OnlyShowIn=Old;" entry to the legacy 
              hierarchy, and a new-style desktop entry to 
              datadir/applications/, and still get 
              only one entry in the menus.