Click on the pane you wish to delete.
Note: The selected pane is highlighted with a light blue border.
 
| 
 | 
| (Top pane is highlighted) | 
Press the Delete key.
OR
 
Right-click on the pane you wish to delete to display the context menu.
 
Select Delete Pane.
OR
Right-click on the pane you wish to delete to display the context menu.
 
Select Cut, then select Pane.