I can't reproduce your problem. I opened menulibre in a XFCE session. For "xfce window manager ,window tweaks and workspace" i added additionally under "Only show in" LXDE. And all three menu entrys show up in a LXDE session, under settings. You should check your start menu under LXDE. There is now a new "folder" named "Settings" with all 3 entries.
If they don't show up you have maybe screwed your installation.
fadi wrote:I do not think it is well tested or well integrated into the system.
Well...naughty!