DUAL BOOT ARCH AND WINDOWS

NOTE: this method applies only to systems booting up with systemd-boot, NOT GRUB
 

First off, mount Window's EFI partition:

mount /dev/sdXN /mnt

 
Copy /mnt/EFI/Microsoft folder contents into /boot directory:

cp -r /mnt/EFI/Microsoft/ /boot/EFI/Microsoft/

 
Add a new entry for Windows by editing the /boot/loader/entries/windows.conf file:

title   Windows 10
efi     /EFI/Microsoft/Boot/bootmgfw.efi

 
Apply changes:

bootctl update

 
Check that the new entry is showing correctly with:

bootctl list

 
It should show something like this:

Boot Loader Entries:
        title: Arch Linux
           id: arch.conf
       source: /boot/loader/entries/arch.conf
        linux: /vmlinuz-linux
       initrd: /initramfs-linux.img

        title: Windows 10
           id: windows.conf
       source: /boot/loader/entries/windows.conf