If rEFInd works it is probably the best, easiest, and most reliable option. Sometimes a work around is the best you may get.
You can try "blessing" the MS bootloader. I've used this to create some custom macOS and Linux boot disks. You need to do this from macOS. You first need to mount the hidden ESP/EFI partition on the Windows boot drive.
Then you need to launch the Terminal and use the "bless" command using the following format which you will need to customize for your drive since I do not have an actual Windows drive to give you specifics. I'm just doing this from memory so I may have the folder structure slightly off, but you should be able to figure it out.
sudo bless --folder /<mount-for-Win-ESP>/EFI/Microsoft/ --file /<mount-for-Win-ESP>/EFI/Microsoft/<somename>.efi --label "Win10" --shortform --verbose
or possibly:
sudo bless --folder /<mount-for-Win-ESP>/EFI/boot/ --file /<mount-for-Win-ESP>/EFI/boot/<somename>.efi --label "Win10" --shortform --verbose
If you want to set the NVRAM to boot Windows as the default then add on the following option "--SetBoot".
There will be at least two files in these folders which have the ".efi" extension. I really do not know which one is best to use. I am fairly sure I've used both to boot Windows. Make sure to select only one folder and file when you "bless" it or you will end up with multiple boot options on the Apple boot picker menu.
rEFInd and "bless" are your two best options.
