Кусок из доки по syslinux:
Код:

MENU BEGIN [tagname]
MENU END
Begin/end a submenu. The entries between MENU BEGIN and MENU
END form a submenu, which is marked with a > mark on the right
hand of the screen. Submenus inherit the properties of their
parent menus, but can override them, and can thus have their
own backgrounds, master passwords, titles, timeouts, messages
and so forth.