Bonjour,
Some applications do appear in the global xfce menu.
For instance, I installed aegisub and mkvtoolnix-gui, both have a "desktop" file in /usr/share/applications/ directory:
org.aegisub.Aegisub.desktop
org.bunkus.mkvtoolnix-gui.desktop
But they do not appear in the menu.
Thank you.
F.P.
On f42 (they used to be there on f40)