Comment 8 for bug 1089438

I have improved the patch. Instead of being stuck between XFCE and Others - it now checks whether the desktop environment is LXDE as well.

        if os.getenv("XDG_CURRENT_DESKTOP") == "XFCE":
                process = subprocess.Popen(['exo-desktop-item-edit', file_path], env=os.environ)
        elif os.getenv("XDG_CURRENT_DESKTOP") == "LXDE":
                process = subprocess.Popen(['exo-desktop-item-edit', file_path], env=os.environ)
        else:
                process = subprocess.Popen(['gnome-desktop-item-edit', file_path], env=os.environ)
        GObject.timeout_add(100, self.waitForNewMenuProcess, process, parent.get_menu_id(), file_path)

It has been applied to

1. New Item
2. New Menu Item
3. Edit Properties
Same instructions, make a backup of /usr/share/alacarte/Alacarte/MainWindow.py and then replace it with the patch.