How to remove Hyper V boot "Files" from the Boot order (under "Firmware" menu in Settings)

(Courtesy of https://sandyzeng.com/hyper-v-remove-firmware-file-bootmgfw-efi/) 

Here is the simple way delete all the bootmgfw.efi file at once. Use powershell.

$VMName = "Your virtual machine name"
Get-VMFirmware -VMName $VMName |ForEach-Object {Set-VMFirmware -BootOrder ($_.Bootorder | Where-Object {$_.BootType -ne 'File'}) $_ }