Then the XFCE patterns probanly don’t require it. I have a Leap 16.0 VM with KDE and Myrlyn is installed. A quick search tells that restarting the panel could work, and also rm ~/.config/menus/xfce-applications.menu followed by a logout + login.
xfce seems to be the poor cousin in 16, yet I find it by far the most productive (least distracting) desktop. I shjall revert to 15.6 in order to get the work done.