grub: Menu entry editor
14.3 Editing a menu entry
=========================
The menu entry editor looks much like the main menu interface, but the
lines in the menu are individual commands in the selected entry instead
of entry names.
If an <ESC> is pressed in the editor, it aborts all the changes made
to the configuration entry and returns to the main menu interface.
Each line in the menu entry can be edited freely, and you can add new
lines by pressing <RET> at the end of a line. To boot the edited entry,
press <Ctrl-x>.
Although GRUB unfortunately does not support "undo", you can do
almost the same thing by just returning to the main menu using <ESC>.