Hi,
Not familiar with the Yoga BIOS,
But on my HP Netbook which also uses mmc disk, I have "2 places" to set the "boot disk", 1 in the disk priority in the main bios,
and another, in my case a F9 "Boot Disk" selection with only 2 options "EFI File" or "Hard Disk"
May not be the same for you, but worth checking...
GL