@CCWieland ,
Yes, it is a bit tricky and I haven’t played around with it much, but there is a hierarchy that you’ll have to work through. For instance:

I can’t override the Material, I first need to overridethe Linked Suzanne and then I can select the Material in the Outliner and right click to:

I tend to do this from the Outliner, then I can easily see what is already overriden and work my way down, but I guess there are other ways…
Selected and Content doesn’t always do what I would expect, so I usually just choose Selected.