Comment # 3 on bug 1076779 from Dominique Leuenberger

Reproduced this locally - the result was the same as on openQA: post
installation, Windows 10 was not listed in the boot menu

upon booting up the Tumbleweed installation, I issued the command 'os-prober'
which responded with:

/dev/vda2@/EFI/Microsoft/Boot/bootmgfw.efi:Windows Boot Manager:Windows:efi

(so windows 10 partition seen)

rerunning grub2-mkconfig > /boot/grub2/grub.cfg from within the TW installation
rewrites the grub menu with a Windows Boot Manager added back.