Gtk-shell-shows-menubar=trueHere are step by step instructions for doing this. for MATE, you'll need to edit the ~/.config/gtk-3.0/settings.ini file (if this file doesn't exist, create it) and in this file, add the following under '': Xfconf-query -c xsettings -p /Gtk/ShellShowsAppmenu -n -t bool -s trueДў.B. Xfconf-query -c xsettings -p /Gtk/ShellShowsMenubar -n -t bool -s true This doesn't occur with Numix GTK theme (which is installed by default in Xubuntu) or Greybird in Xubuntu 16.10.Дў.A. For example, the menu font is dark on a dark panel background using the default Xubuntu 16.04 theme (Greybird). there's no way of changing the global menu font color, and that can be problematic with some themes.MATE only: there's no easy way of moving the applet to the desired position, but it can be done using Dconf Editor.If someone can find a way to solve this, please let us know in the comments! MATE only: GTK2 applications have the menu displayed on both the panel and in the application window.This doesn't occur if the appmenu-qt5 package is installed though

Qt5 supports the AppMenu feature by default, without using any additional packages (I'm not sure which version introduced this feature), however, there's a bug with this and Vala AppMenu which causes the global menu for Qt5 applications to be displayed for a few seconds after the app is closed.

These menu items don't work, at least in Ubuntu, and using them can cause the Xfce / MATE panel to crash

when no window is focused / the desktop is empty, a menu containing 'Desktop' and 'Files' is displayed by the Vala AppMenu applet.

Vala Panel AppMenu is not perfect though, and I did encounter a few issues in my test:

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