I followed this guide to install Windows 10 on an external USB drive. It all works great.
The way to allow the Mac to boot is as follows
(this is done inside the command line when booting from the Windows installer USB):
To make your installation bootable,
enter bcdboot W:Windows /l en-us /s Z: /f UEFI. This will create the boot files in your EFI partition.
From what I understand, the Mac has a partition where UEFI systems can boot and in this particular case boots Windows from that partition and then control is passed to whatever is located on the external drive. I became aware of this here.
I would like to be able to boot this Windows installation from other Macs without running the
bcdboot command as that would imply booting the Windows installer and running cumbersome operations.
I also know that a USB stick can boot the system (this is what macOS installer and Windows installed do). So… my question is this:
Can you create a USB stick that boots up the system and passes control to my USB drive with Windows installed on it? Or maybe change the Windows USB drive to allow it to boot?
I don’t understand the whole booting process but my guess would be that a bootloader could be installed on a USB stick and that would allow me to boot Windows.