Thanks for the heads up, ArNeo.
The new controls have made it a little more challenging to implement the previous grid's functionality for the first group header cell. Due to time restraints, I need to revisit it at a later time. In the meantime, I've left it turned off in that cell and removed the tool tip altogether. For now, as Pfeil had mentioned, you'll either need to right-click and select, 'expand/collapse all' or use the feature in the other cells (kind of like a hidden feature now as it stands).
Sorry about that!