Hi @Andrew Tabar ,
there is a way and it involves either a bit of scripting or some MP authoring. SCOM has some nice PowerShell cmdlets, but when it comes to group editing, there is more to wish. So I would recommend you to go this way:
OpsMgr: How to create a group of all Windows Computers that are NOT a member of another group
https://kevinholman.com/2012/03/09/opsmgr-how-to-create-a-group-of-all-windows-computers-that-are-not-a-member-of-another-group/
You can apply the same logic in your case and achive the task.
I hope I could help you out!
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Regards
Stoyan Chalakov