Change GRUB Default OS on Ubuntu Guide
You Are Welcome! The Tutorial shows you Step-by-Step How to Change GRUB2 OSes Boot Entries Order in Ubuntu GNU/Linux Desktops.
And this Ubuntu GRUB Boot Setup make use of the Grub Customizer Graphical UI.
Especially relevant: also if you can directly edit the GRUB Configuration Files on the Command Line this Tool is very useful and valuable to easily manage and dive into the tricky Grub2 Configuration.