in the applications menu which is invoked by clicking with the right mouse button on the desktop shows the shortcuts which are not displayed in xfce. Classic menu and whisker menu so these shortcuts as you need-not displayed. Not sure I picked the right category for the bug
In this menu, you can see the shortcuts with the parameter NotShowIn=XFCE;
I can confirm that the menu shows all applications.
Created attachment 8524 patch Note: the argument is used to pass a fallback variable. https://git.xfce.org/xfce/garcon/tree/garcon/garcon-environment.c#n82
Theo Linkspfeifer referenced this bugreport in commit f498ee7468d57c352e4edd89a945ec198c6c9e0d Set desktop environment for garcon app menu (Bug #14599) https://git.xfce.org/xfce/xfdesktop/commit?id=f498ee7468d57c352e4edd89a945ec198c6c9e0d
LGTM, thanks.