-EDIT- I got it working; see reply #2 but leaving all of this for anyone searching the same issue in the future.
Trying to image an existing Windows 10 installation into a bootcamp partition; using WinClone 7. The screenshots on the tutorial look like they’re from an older version, so I’ve been guessing my way through this.
What I’ve tried:
I have a cloned image of my Windows 10 installation; ran SysPrep on PC, tried to do Volume to Volume cloning and this failed.
I booted Windows 10 from a USB drive on the MacBook and it ran just fine; so I booted back into Mac OS Mojave and created an “Image from Volume” in Winclone. I then restored this image to my bootcamp partition and got the “missing bootmgr” error.
Next step, I booted back into Windows 10 via USB and ran SysPrep on the drive again, went back into Mac OS and created a Winclone image of the drive in this state. I then restored this version of the image to my bootcamp partition. Once again I get the missing bootmgr error.
I then booted into a recovery disk for Windows 10 and opened a command prompt to rebuild the BCD; it finds the windows installation but the rebuild option then fails saying it can’t access the drive.