So, I had to reinstall windows as a dualboot, because I need some CAD tools for work. It was painful but it's not thebaubject
I'm running nixos with systemd-boot and I installed windows on another drive. I started to research how to add the entry on the boot list so I don't need to go in bios to switch the boot order each time I want to change OS.
Most of the information I find is about grub on nixos but I finally find information on how to add a manual entry. On the Arch wiki I find some information but now I have to blend all that to make it work on my laptop.
It's late and I'm scared to mess up my boot partition so I go to sleep to work instructions on it the next day.
The next day I'm ready to do all that only to realized that there is already the entry for windows is already in the boot menu, it has been added automatically.
So I spent all this time to think about how I while have to adjust my system manually only to realize that nixos already did it automatically for me.
Assuming that you are dualbooting from a single storage device - If you have some money to spare go and buy a second ssd. Keeping both OSes in separate storage devices will result in far lesser chances of screwing up.
Though take heed for windows will always find a way to mess up your bootloader.
install linux After Windows and with its own boot partition. if it has foreign OS probe it finds windows and adds a chainloader grub entry. Set linux as default in bios. Windows never knows it is chainloaded and leaves your linux boot alone
This is what I did, I prepared a partition for windows on the second ssd and it went OK.
The only issue was that I needed to manually add drivers on the windows usb for it to be able to recognized my ssd. It was a bit of a pain to find this information online