I know you can do something like bcdboot.exe /m {aaaaaaaa-bbbb-cccc-dddd-eeeeeeeeeeee} to force your own but for some reason when I try that, it still assigns it's own anyway. I know there are ways to assign OS loader GUID outputs from bcdedit to a variable in batch but I am wondering if there is a similar method in bcdboot?bcdedit GUID to variable batch example:
For /F "tokens=2 delims={}" %%i in ('bcdedit.exe') do (set _NEWGUID=%%i)