there was one time that I used a program to modifying UEFI boot loader,
but accidentally removed default boot loader of win10,
then I surfed the internet for resolution,
but failed because Microsoft's variety of versions
finally, I found it.
https://thinker-evans.blogspot.com/2020/02/windows-10-uefi-bootloaderwindows-10.html
Here's the point:
After Windows 10 1709, bootrec /fixboot is deprecated.
step 1: build usb booting image for windows recovery
step 2: mount usb rod for recovery
step 3: >bcdboot "C:\Windows" /s Z: /f UEFI /l zh-tw
Modify disk code for your situation