Grub is a bootloader. It is not meant to work from the menu. Grub is used
only when you re-boot and displays briefly so that you can choose which OS
to boot.

The problem isn't with the Ubuntu menu, but with your expectations and lack
of understanding.

Some things will never display in the menu, They are not meant to be used
from a menu. In the case of Virtualbox it was because of an installation
problem. In the case of Grub it is a bootloader and only can run when you
boot. You can edit Grub using various applications but you cannot run it.

You are assuming too much and the worst thing is that you are assuming
something is broken when it isn't. Instead think that if something is not
working it is for a valid reason and then try to find the reason. Helping
someone when you can't see their computer, what they've done or what they
haven't done is difficult enough. Adding to the difficulty by trying to do
things that no Linux user would do is and jumping to conclusions makes it
next to impossible.

As for Grub itself what is not happening that you want to happen? You can
edit grub quite easily with any text editor. You can change the drive,
partition, parameters and default boot order. seldom you need to rewrite
Grub unless it has been written over by Windows or is on the wrong drive.