Yes, fascinating possibilities.
Ramachandra has been posting in another thread about unable to multiboot on his new HP laptop:
viewtopic.php?f=63&t=2593
He created an esp fat partition for a frugal install of EasyOS, and by pressing F9 key at bootup, got a list of boot options and was able to choose which one to boot.
However, the F10 key brings up UEFI-BIOS setup, and it has no way to change the default boot choice. It stays stuck on Windows.
Ramachandra reports that many others have complained about this, and on the Internet he found a solution. This is his email to me:
Nothing worked to get the refind.conf menu upon booting my HP Laptop, as a last resort I have attempted some work around in the Microsoft EFI folder. As per suggestions from Internet, I have copied BootX64.EFI from EFI folder of easyos and put it on Windows EFI (EFI/MICROSFOT/BOOT/BOOTMGFW.EFI) and renamed bootex64.efi to bootmgfe.efi. then rebooted the system. Now, Laptop boot into EFI of easyos. (Still as informed easyos is not booting). Moreover, no menu entry for Antix Linux. The menu entry is given below;-
Boot Fall back boot loader (Partition label SYSTEM)
Boot Vmlinx (Partition Label Easy)
Boot Fall back Boot loader (partition Label Easy)
About Refind
Shutdown
Reboot
Reboot to Computer Setup Utility.
If pressed Boot Fall back boot loader (partition System) goes to Windows and If pressed to Boot vmlinux (Parathion label Easy) booting EasyOS.
If pressed Boot Fall Back Boot Loader (Partition Label Easy) it goes to Refind and listing new Menu page like
EASYOS BOOT MENU
Boot EasyOS 2.7.3. (partition Easy)
Boot Antix Linux (Partition Antix)
Shutdown
Reboot
Why Antix Linux not listing first instance upon booting?. May be due to windows efi effect. Any other trick.
I am surprised that Windows, in doing a self-check, doesn't throw a tizzy-fit seeing it's BOOTMGFW.EFI replaced.
I haven't replied to ramachandra yet, but it looks like the first menu is because BOOTX64.EFI, which is actually refind, cannot find a 'refind.conf' file. That would also need to be copied, and edited to show the Windows boot option.
That 'bcdedit' in the first link, looks good.