grub2list.sh

#!/bin/bash

awk -F\' '$1=="menuentry " {print i++ " : " $2}' /etc/grub2.cfg

edit 'GRUB_DEFAULT= XX' on '/etc/default/grub'

or

$ sudo grub2-set-default XX

$ sudo grub2-editenv list

or

$ sudo grub2-editenv list

$ sudo grub2-reboot 0