The reason this doesn't work
'set TCAdditem1= TestConfigFact.Additem(Null) 'TCAdditem1.TestConfigList.Field("TSC_USER_01").Value = "Hoch" 'TCAdditem1.TestConfigList.Item(1).Field("TSC_USER_01").Value = "Hoch"
Is because the AddItem method is used to create a whole new entity - in this case a whole new Test Configuration entity. You don't want to do that. You want to modify the Test Configuration that already exists.
That is the same reason your second try didn't work.
'set TCAdditem2 = TestConfigFact.Additem(Null) 'TCAdditem2.TestConfigList.Item(1).Field("TSC_USER_01").Value = "Mittel"
Your third try has a similar reason for not working, though in this case you tried to add a new item to your list.
'set TCAdditem3=TestConfigList.Item(1).Additem(Null) 'TCAdditem3.Field("TSC_USER_01").Value = "Niedrig" 'TCAdditem3.Field("TSC_USER_01")="Niedrig"
Your last try - AddItem is not something you can do to a Field.
'set TCAdditem = TestConfigList.Item(1).Field("TSC_USER_01").Additem(Null) 'TCAdditem.value = "Niedrig" 'TCAdditem = "Niedrig"
Using one of these lines, plus the Post method, should've worked.
'TestConfigList.Item(1).Field("TSC_USER_01").Value= "Mittel" 'TestConfigList.Item(1).Field("TSC_USER_01") = "Hoch" 'TestConfigList.Item(1).Post
I tried them myself and they didn't work for me either. I'll have to take more time to try to figure out why.