<p>I would like to be able to set "Extend my Windows desktop onto this monitor" via code. A PowerShell script would be ideal. WMI seems the way forward but I have zero knowledge in WMI.</p>

One first possible solution is... through the GUI (but without user interaction)
VB script
(also
described here
but in
Autoit
language):
```
```
Option Explicit
Dim WshShell, Dummy, Splash

On Error Resume Next

Set WshShell = WScript.CreateObject("WScript.Shell")

'Main
Call DoIt
WScript.Quit

Sub DoIt
wshshell.Run("%systemroot%\system32\control.exe desk.cpl,@0,3")

' Give Display Properties time to load
WScript.Sleep 1000
WshShell.SendKeys "2"
WScript.Sleep 10
WshShell.SendKeys "%E"
WScript.Sleep 500
WshShell.SendKeys "%A"
WshShell.SendKeys "{TAB}"
WshShell.SendKeys "{TAB}"
WshShell.SendKeys "{TAB}"
WshShell.SendKeys "{TAB}"
WshShell.SendKeys "{TAB}"
WshShell.SendKeys "{TAB}"
WshShell.SendKeys "{TAB}"
WshShell.SendKeys "{TAB}"
WshShell.SendKeys "{TAB}"
WshShell.SendKeys "{TAB}"
WshShell.SendKeys "{ENTER}"
End Sub 'DoIt
```
```
In Autoit, that would be:
```
```
;
; — toggle-screen.au3
;

; exec cpanel app `display settings`
Run(”C:\WINDOWS\system32\control.exe desk.cpl,@0,3?”)

; wait for window to be active
WinWaitActive(”Display Settings”)

; select 2nd display
Send(”{TAB}”)
Send(”{DOWN}”)

; work back to the ‘extend desktop’ control
Send(”+{TAB}”)
Send(”+{TAB}”)
Send(”+{TAB}”)
Send(”+{TAB}”)
Send(”+{TAB}”)
Send(”+{TAB}”)
Send(”+{TAB}”)
Send(”+{TAB}”)
Send(”+{TAB}”)

; toggle ‘extend desktop’ control and apply
Send(”{SPACE}”)
Send(”{ENTER}”)

; wait for window to be active
WinWaitActive(”Display Settings”)

; accept
Send(”{TAB}”)
Send(”{ENTER}”)

;
; — E.O.F.
;
```
```