Some applications display their menus (File, edit, etc.) in Unity but not in Xfce. Some example screenshots from Unity:
However, these applications don't display these menus in Xfce. I have enabled a global TopMenu on Xfce, but that does not make these applications display their menus.
Since these very same applications do display these menus in Unity, they are indeed available. But how can I enable them in Xfce?
I have read "Application menus missing in Xubuntu" and "How do I display google chrome's menus in xubuntu? I can't find them". There are no suitable answers there. Also, this question is about the general phenomenon, not just the individual apps. Also, I want to specifically emphasise that these menus do appear in Unity, which means that they are indeed available.