How to configure the RDP connection for Azure VMs via Azure Bastion

In my script before I connect, I kill the RDP session. Locate the RDP file and mod it.
(Get-Content $ConnRDPNQ).Replace("use multimon:i:1", "use multimon:i:0") | Set-Content $ConnRDPNQ

$ConnRDPNQ is the location of the .con file.

After the mod, I use:
Start-Process -FilePath "$env:windir\system32\mstsc.exe" -ArgumentList "$ConnRDP /prompt"

Now the RDP session starts with a single screen.

With: Start-Process -FilePath "$env:windir\system32\mstsc.exe" -ArgumentList "/l"
You get a pop-up with your screen ids, Because you can also set the RDP to use 2 out of 3 screens.
So on my workplace My screens are 4 and 5 they need to be comma seperated

Add-Content $ConnRDPNQ -value "selectedmonitors:s:$screenselect"
In this case $screenselect should be 4,5 making this: 
Add-Content $ConnRDPNQ -value "selectedmonitors:s:4,5

Now when I start
Start-Process -FilePath "$env:windir\system32\mstsc.exe" -ArgumentList "$ConnRDPNQ /prompt"
My laptop screen "normal" and the monitors on the dock are used by the RDP session