External Boot Camp partition doesn't show up in Startup Manager


I have created an Winclone image from an internal Boot Camp partition and have restored that image to an external exFAT hard drive partition following this guide, except for that I have not used Sysprep. Now, I want to boot to that external partition, however, when I boot into the Startup Manager pressing the Alt key during startup, I don’t see the created external Boot Camp partition in the list. I have also enabled booting from external media in the Startup Security Utility but with no effect.

Could you please help me make the external Boot Camp partition show up in the Startup Manager so that I can boot into it? I am using Winclone 7.3.2 with macOS Mojave 10.14.5 on a 13-inch MacBook Air 2018. The Boot Camp partition runs Windows 10 (1809 update). The external drive is connected via USB-C to USB-A adapter.

Thanks in advance.


Regardless of anything else, it should definitely show up when holding down the option key. We have tested the 2018 MacBook Air (T2) with a USB-C drive and windows 1809 and it does boot externally for us. All the files that make it boot are on the EFI partition. Can you try and mount the EFI partition on the external drive and see if the Windows boot files are there? For example, if the external drive is /dev/disk1, mount efi by running:

sudo diskutil mount /dev/disk1s1

Then an EFI volume should mount on your desktop.