A chart can have multiple topmost boxes, like these.
To create multiple topmost boxes:
1 Add 2 co-workers to the topmost box.
2 Select the 3 topmost boxes.
3
Select Chart Styles
from the Format menu and select
the Co-Manager Style 
option. The selected boxes are now represented
as co-managers.
4 Select the topmost lines and select Hide from the Format menu.
