I am glad that it helped you JGrote ! 🙂
Follows how I expanded the msix file to vhds:
# size of the vhdx file
$vhdSize = 3100
# folder that will created inside the vhdx (You can get this name from the manifest file or via Get-AppPackage)
$appParentFolder = "SSMS"
# vhdx destination. Notice that I am using the appParentalFolder to set the name
$vhdFullPath = "C:\msix\avd\vhdx\$appParentFolder.vhdx"
#application package name that can be obtained in the appxmanifest.xml or Get-AppPackage -> Full Package name
$packageName = "SSMS_1.0.3.0_x64__kz5d2ck10dqg4"
# msix file
$msixPath = "C:\msix\avd\msix\SSMS_1.0.3.0_x64__kz5d2ck10dqg4.msix"
#Expand the MSIX to VHDX
cd "C:\msix\avd\msixmgr\x64\"
.\msixmgr.exe -Unpack -packagePath $msixPath `
-destination $vhdFullPath `
-applyacls -create -vhdsize $vhdSize -filetype "vhdx" -rootDirectory $appParentFolder