My first post on this forum is for you.
No such partition during batocera hd edition in gruboot sequence for me...
But I am able to have a working dualboot with batocera and win10 on a 250Go SSD installed on internal M2 port using the easy routines of usb bootable launchers.
What you need:
1 machine under win for the creation of the 4 bootable medias
android_x86 8.1rc3 iso
windows 10 iso
the destination machine, boot on usb first
_some time (not too much...1h)
_Boot batocera usb media and install bato on ssd via routine (internet needed), shutdown, remove usb media, restart in fresh SSD bato installation, shutdown.
_Boot gparted usb media, liberate free space for the windows partition by reducing the end of the "share" partition, create a new ntfs partition in this space, shutdown, remove usb media.
_Boot android_x86 usb media, select install, select the fresh partition, during the routine, select do not format, transform gpt to mbr (don't care about the warning), install grub and select an entry for windows (which will be batocera), finish the install, shutdown, remove usb media.
Restart, and at this moment, you've got a working multiboot with 3 androids and 1 windows (which is batocera), try it, shutdown
Boot windows usb media, install on the androided fresh partition without format, remove usb media after reboot, finish the install, reboot.
No more dualboot, start in windows. You can remove grub and android folders
Install grub2win, launch it, add a new entry, edit by selecting an debian entry, name it batocera, select the share partition (can't select others), apply, close grub2win
Open c:/grub2/grub.cfg with notepad, search the new batocera entry,
remove the 4 first lines with words "root" or "uuid"
modify the 5th line with the word "root" to:
linux /vmlinuz verbose nomodeset
add a line:
Save, close notepad, restart.
Enjoy your brand new dualboot, press a key to start if ask
(Maybe someone could improve the grub.cfg for us, to remove the warning about "disk adress" in grub2win)