bcdedit /set GUID device partition=D: bcdedit /set GUID osdevice partition=D: bcdedit /set GUID path \Windows\system32\winload.efi bcdedit /displayorder GUID /addlast

bcdedit /enum Or for a cleaner view:

Note: Easier to use GRUB. But for direct boot:

bcdedit /create /d "Windows 10 on D:" /application osloader This returns a GUID like xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx . Copy it.