BootSelector is a tiny GUI utility for setting any grub menu entry as default.
It also allows you to reboot into any OS/kernel in your grub menu.
The initial version has been tested on the latest Ubuntu 24.10 and should work on other Debian-based distributions as well.
An RPM for fedora will be released soon after more testing is done.
No. It just reads and parses the contents of /boot/grub/grub.cfg and updates /etc/default/grub
but then how does it override the default only once?
It uses grub-reboot for that function.