First off, grub supports rebooting in to a specific OS, so you might want to use that instead. See https://unix.stackexchange.com/questions/43196/how-can-i-tell-grub-i-want-to-reboot-into-windows-before-i-reboot for more details.
To add an extra button would require to edit the source code of Pantheon, which would require that you manually compile Pantheon ...
My main problem was that I was unable to access BIOS, as the normal method for my laptop didn't work (i.e. when laptop is OFF, press & hold F2 and turn it ON, keep holding F2 until bios shows up). However today after some new desperate attempts with boot-repair, I tried enter BIOS the way it's normally done on other laptops (i.e. turning it on ...
THIS SOLVED MY PROBLEM, THANKS!
Shut down your Mac.
Locate the following keys on the keyboard: Command (⌘), Option, P, and R.
Turn on your Mac.
Press and hold the Command-Option-P-R keys immediately after you hear the startup sound.
Hold these keys until the computer restarts and you hear the startup sound for a second time.
Release the ...
I've looked into Rufus documentation and found this:
I used an UEFI bootable ISO based on grub, but all I get is the grub prompt
This can happen if you chose GPT partition scheme for UEFI computer in the Partition scheme dropdown, and part_gpt module was not included in grub when running grub-mkimage (See here).
In this case, you need to select MBR ...