As far as I can tell, you don't need the comma after "close". So you do {'Gtk/DialogsUseHeader': <0>, 'Gtk/ShellShowsAppMenu': <0>, 'Gtk/DecorationLayout': <'close:menu,maximize'>} and it works
Just as a note, if we set the button layout in org.gnome.desktop.wm.preferences it *does not* have the desired effect.
I can confirm that this works.
As far as I can tell, you don't need the comma after "close". So you do {'Gtk/DialogsUs eHeader' : <0>, 'Gtk/ShellShows AppMenu' : <0>, 'Gtk/Decoration Layout' : <'close: menu,maximize' >} and it works
Just as a note, if we set the button layout in org.gnome. desktop. wm.preferences it *does not* have the desired effect.