Toggle Windows Defender real time protection via Desktop shortcut

It seems you can do this in powershell:

Set-MpPreference -DisableRealtimeMonitoring $true

Obviously, set it to $false to turn it back on.

This answer on StackExchange discusses how to turn this into a shortcut if that's how you choose to proceed.

To actually toggle the real-time monitoring state put the following in a PowerShell script (must be run as administrator):

$preferences = Get-MpPreference
Set-MpPreference -DisableRealtimeMonitoring (!$preferences.DisableRealtimeMonitoring)

To make this into a desktop shortcut, right-click on the Desktop, choose "New" and then "Shortcut" and enter the following for the item (substituting the location of the script you created for the -File argument)

%SystemRoot%\system32\WindowsPowerShell\v1.0\powershell.exe -ExecutionPolicy Bypass -File "C:\Users\yuji\Documents\toggle-monitoring.ps1"

And in the Advanced options, enable Run as administrator.