How to add something to the panel from the "choosable" options (predefined stuff) via terminal command?

How to add something to the panel from the "choosable" options (predefined
stuff) via terminal command?

I know how to add the "terminal" icon to the panel like this:
cat > /usr/share/applications/11.desktop << "EOF"
[Desktop Entry]
Exec=gnome-terminal
Type=Application
Icon=/usr/share/icons/gnome/scalable/apps/utilities-terminal.svg
EOF
/usr/libexec/gnome-panel-add
--launcher="/usr/share/applications/11.desktop" --panel="top_panel"
--position=900
but the question is, how do you add something like..
MAIN MENU
to the panel ?
there is no path to it, there is no icon to it, there is no "properties"
to it..
nothing to work with.
MAIN MENU
is a choose-able thing within the "Add to Panel" options.
there are few things that can not be done via the code above.
how do i add these objects via terminal command ?