This post is an update (using Windows 10 and a newer version of Convert-WindowsImage.ps1) of a similar post I had in my blog about booting natively from a .VHDX file:
https://devblogs.microsoft.com/cesardelatorre/booting-windows-8-1-update-natively-from-a-vhdx-image/
I’m also publishing this for my own records and folks asking me about it...