The problem is to make the “BIOS EFI ENGINE” to see EFI file on a disk. Perhaps I already mention that I am unaware of any linux tool to strip NVRAM. PC makers frequently collaborate with software companies to “accommodate” their equipment so it is going to be used with “proper” software. Usually “BIOS EFI ENGINE” see bootx64.efi localized in EFI folder on separate efi partition (in Linux it is frequently /efi/boot/EFI). So if this file is not yet present there you can copy your windows efi file (whatever name and location) to EFI folder and then rename it into bootx64.efi. The “BIOS EFI ENGINE” may show the menu at start or may not it depends. You might use efibootmgr when logged into opensuse (see above). If this does not work then use GRUB2 to start Windows as explained above. I warn you that you have to learn a bit about GRUB scripting since GRUB2 is a kernel by itself.