At least we have installed more than one operating system on our laptop. then we will continue our favorite boot operating system to become the default operating system on boot grub. In this tutorial I use Windows 10 and Parrot OS. And it will make Windows 10 the default boot on my laptop. The following results
1. Log in as a super user
#sudo su
2. Type this command grep menuentry /boot/grub/grub.cfg
# grep menuentry /boot/grub/grub.cfg
3. Edit file /etc/default/grub, then change the GRUB_DEFAULT value to the image below. Then save the configuration
# nano /etc/default/grub
4. Update grub with the command below
# update-grub
5. Done