How to display more than 8 menu entries?

[Markus Elfring]

Hello,

I get up to eight boot menu entries presented on the graphical user interface at
the moment. But I need more options to select between the bootable systems. I do
not see a command for the specification of a higher limit so far.
http://www.gnu.org/software/grub/manual/html_node/Command_002dline-and-menu-entry-commands.html

I saw that the text user interface can show more menu entries in a (ncurses?)
list box. How can such GUI limitations be adjusted?

Regards,
Markus