Created attachment 3314 add a main category key to desktop files .desktop files in xfce-utils lack the Category key. From the registered categories (http://standards.freedesktop.org/menu-spec/1.0/apa.html) I'd suggest “Utility”, so attached patch does that.
Created attachment 3315 add main category Previous patch was completely not working, this one will do.
Seems to work fine here; applied in 6cb7ef0.
Was too quick with this and didn't noticed the dup in accessories.
What do you mean by "dup in accessories"? The committed patch looks fine to me and desktop-file-validate validates the files correctly. Or I'm missing something?
Forgot the close it, the dups were fixed in http://git.xfce.org/libs/garcon/commit/?id=f64fb983e29ed30c8e1cb32cb66b8a66c03bd247.