I have just upgraded to JabRef 4.0 from 3.8. In the Groups interface, the previous version allowed to select the inverse of the selected group. So, I could select Groups A and B and then selected Inverse to see everything that was in neither A nor B. Is there a way to do that now? Should I create an automatic group with some specific expression? Thanks in advance for any advice. I really need the inverted feature — I use it all the time.