https://askubuntu.com/questions/833006/how-can-i-manually-boot-windows-from-the-grub2-terminal
booting windows from GRUB prompt
GRUB> insmod ntfs
GRUB> set root=(hdX,gptX)
GRUB> chainloader (${root})/EFI/Microsoft/Boot/bootmgfw.efi
GRUB> boot
https://www.ubuntubuzz.com/2016/03/booting-gnulinux-manually-with-grub-prompt.html
booting ubuntu from GRUB prompt
GRUB> ls
GRUB> set root=(hd0,X)
GRUB> linux /boot/vmlinuz-4.2.0-16-generic root=/dev/sdb3
GRUB> initrd /boot/initrd.img-4.2.0-16-generic
GRUB> boot
