I've rigged this face, adding drivers to shape key values and particle systems. So far so good, but when I add drivers to some node values they don't show up in the Grap Editor when viewing Drivers.
If I create an new empty scene and try to reproduce the issue, it's working as suspected. The material show up beneath the object, and I can expand all the driven inputs.
It's just not working in my previous scene with the face :(