If you often need to edit GRUB2 menu entries, you might have used the terminal line by editing some configuration files. That is hectic, and maybe prone to errors. Fortunately, there is a tool that allows editing GRUB2 menu graphically. So not only you will be able to add non-detected OSes, but also submenus, change resolution of GRUB and more.

The latest version of GRUB Customizer contains the following changes and bug fixes:

• add grub customizer to ubuntu official repo
• few strings not translatable
• G.C. removed both entries for a kernel when I unchecked only 1
• Unbuntu Entries Gone from Grub after Ubuntu 11.10 installs updates
• Won't customize grub2 on flash drive
• Grub-customizer fails to load configuration when starting application
• GRUB Customizer 2.5.5 (GC) generates file grub.cfg with error in command gfxmode
• update-grub#: command not found
• Can't select non-system partition for grub
• application does not update; only default grub menu appears
• Incorrect FSF address in sources
• gfxmode vga=788 is depreciated

To install Grub Customizer in Ubuntu based distros:

sudo add-apt-repository ppa:danielrichter2007/grub-customizer
sudo apt-get update
sudo apt-get install grub-customizer