That's pretty straight forward.
Originally Posted by cipherboy_loc
Open a terminal.
Paste this in:
Make these lines look like this:
sudo nano /etc/default/grub
Hit Control+x then 'y' to save and exit. Reboot. You should get the menu for ten seconds (indefinitely if you then hit any key).
It might be a good idea to make a backup before you begin in case you make any mistakes:
Grub Customizer is the non-terminal way of doing this but not sure if there is an ISO or if you can install it to a Live boot (you can with Boot Repair but that won't help here ... yet).
sudo cp /etc/default/grub /etc/default/grub.bak