I have a workaround. I added the following line to .config/lxsession/LXDE/desktop.conf
[Environment_variable] XDG_DATA_DIRS=/usr/local/share:/usr/share:/usr/share/gdm:/var/lib/menu-xdg:/usr/local/share/:/usr/share/:/usr/share/gdm/:/var/lib/menu-xdg/:/var/lib/flatpak/exports/share:/home/ricanlinux/.local/share/flatpak/exports/share Now the discard appears in the menu launcher.
