Powershell script to disable Windows Surface internal Hello camera when an external IR camera is present. I'm using this on a Surface Laptop. Use the XML to import a scheduled task (RunAs should be an Admin on the device).

Windows Hello Camera Switcher.ps1

## Script Specific configuration
$ExternalCameraFriendlyName = "RGB-IR Camera"

## Generic configuration
$Verbose = $true
$Debug = $false
$WhatIf = $false

### END CONFIGURATION #####
$basePath = $MyInvocation.MyCommand.Path.Replace($MyInvocation.MyCommand.Name,"").SubString(0,($MyInvocation.MyCommand.Path.Replace($MyInvocation.MyCommand.Name,"").length-1))
$baseName = $MyInvocation.MyCommand.Name.Remove(($MyInvocation.MyCommand.Name.Length-4),4)
$Transcript = !$WhatIf
if ($Transcript) {Start-Transcript -Path "$($basePath)\$($baseName)-$($env:USERNAME).transcript.log" -Append -Verbose:$Verbose}

if (($CurrentStateExt = Get-PnpDevice -Verbose:$Verbose| Where {$_.FriendlyName -like "RGB-IR Camera" -and $_.Manufacturer -notlike "Microsoft"}).Present -notlike 'True') {
    Write-Verbose "External Windows Hello Camera is unavailable." -Verbose:$Verbose
    switch ((Get-PnpDevice -Verbose:$Verbose | Where {$_.FriendlyName -like "Microsoft IR Camera Front"}).Problem) {
        "CM_PROB_DISABLED" {Write-Verbose "Enabling the internal Windows Hello Camera." -Verbose:$Verbose
                            Get-PnpDevice  -Verbose:$Verbose| Where {$_.FriendlyName -like "Microsoft IR Camera Front"} | Enable-PnpDevice -Verbose:$Verbose -Confirm:$false -WhatIf:$WhatIf
                           }
        "CM_PROB_PHANTOM"  {}
        "CM_PROB_NONE"     {Write-Verbose "The internal Windows Hello Camera is already enabled." -Verbose:$Verbose}
    }
} else {
    Write-Verbose "External Windows Hello Camera is available." -Verbose:$Verbose
    switch ((Get-PnpDevice -Verbose:$Verbose | Where {$_.FriendlyName -like "RGB-IR Camera" -and $_.Manufacturer -like "Microsoft"}).Problem) {
        "CM_PROB_DISABLED" {Write-Verbose "The internal Windows Hello Camera is already disabled." -Verbose:$Verbose}
        "CM_PROB_PHANTOM"  {}
        "CM_PROB_NONE"     {Write-Verbose "Disabling the internal Windows Hello Camera." -Verbose:$Verbose
                            Get-PnpDevice -Verbose:$Verbose | Where {$_.FriendlyName -like "Microsoft IR Camera Front"} | Disable-PnpDevice -Verbose:$Verbose -Confirm:$false -WhatIf:$WhatIf
                           }
    }
}

if ($Transcript) {Stop-Transcript}
break

Windows Hello Camera Switcher.xml

<?xml version="1.0" encoding="UTF-16"?>
<Task version="1.4" xmlns="http://schemas.microsoft.com/windows/2004/02/mit/task">
  <RegistrationInfo>
    <Date>2018-05-25T09:32:30.4538883</Date>
    <Author>Windows Hello Camera Switcher</Author>
    <URI>\Windows Hello Camera Switcher</URI>
  </RegistrationInfo>
  <Triggers>
    <TimeTrigger>
      <Repetition>
        <Interval>PT1M</Interval>
        <StopAtDurationEnd>false</StopAtDurationEnd>
      </Repetition>
      <StartBoundary>2018-05-25T09:31:31</StartBoundary>
      <Enabled>true</Enabled>
    </TimeTrigger>
  </Triggers>
  <Principals>
    <Principal id="Author">
      <UserId></UserId>
      <LogonType>Password</LogonType>
      <RunLevel>HighestAvailable</RunLevel>
    </Principal>
  </Principals>
  <Settings>
    <MultipleInstancesPolicy>IgnoreNew</MultipleInstancesPolicy>
    <DisallowStartIfOnBatteries>false</DisallowStartIfOnBatteries>
    <StopIfGoingOnBatteries>false</StopIfGoingOnBatteries>
    <AllowHardTerminate>true</AllowHardTerminate>
    <StartWhenAvailable>false</StartWhenAvailable>
    <RunOnlyIfNetworkAvailable>false</RunOnlyIfNetworkAvailable>
    <IdleSettings>
      <StopOnIdleEnd>true</StopOnIdleEnd>
      <RestartOnIdle>false</RestartOnIdle>
    </IdleSettings>
    <AllowStartOnDemand>true</AllowStartOnDemand>
    <Enabled>true</Enabled>
    <Hidden>false</Hidden>
    <RunOnlyIfIdle>false</RunOnlyIfIdle>
    <DisallowStartOnRemoteAppSession>false</DisallowStartOnRemoteAppSession>
    <UseUnifiedSchedulingEngine>true</UseUnifiedSchedulingEngine>
    <WakeToRun>false</WakeToRun>
    <ExecutionTimeLimit>PT1H</ExecutionTimeLimit>
    <Priority>7</Priority>
  </Settings>
  <Actions Context="Author">
    <Exec>
      <Command>powershell</Command>
      <Arguments>-File "C:\Scripts\Windows Hello Camera Switcher\Windows Hello Camera Switcher.ps1" -NoProfile -ExecutionPolicy Bypass</Arguments>
    </Exec>
  </Actions>
</Task>