Dragging groups to the Sorter

Hi - Running DT Personal on a Macbook with system software and DT all current versions. I just set up a new database and tried to populate the Sorter with several selections by dragging them to the Sorter pane, however, the Sorter doesn’t recognize them. Suggestions? Thanks in advance for the advice.
Steve

Right now you have to drag & drop each group on its own.