Hi Helmut (@Helmut-72 ),
can you please check this thread and let me know if it helps you ( Iage the feeling that you have the same challenge):
'System' missing in Adminsitrative Templates in GPO n Server 2019 Standard
https://learn.microsoft.com/en-us/answers/questions/334229/39system39-missing-in-adminsitrative-templates-in.html
If you have an older OS (WS 2012 or 2012 R2) this could also be the solution:
Some Group Policy areas are missing from the Group Policy Editor
https://learn.microsoft.com/en-us/troubleshoot/windows-server/group-policy/group-policy-areas-missing?WT.mc_id=EM-MVP-5002219
Hope I could help you out.
(If the reply was helpful please don't forget to upvote and/or accept as answer, thank you)
Regards
Stoyan Chalakov