Groups

You can group basic primitive shapes together
From the Menu Select:
Modify | Group
Hotkey: Control + G

Once your items have been grouped a bounding box appears around it

Ungroup
You can ungroup item by selecting from the menu:
Modify | Ungroup
Hotkey: Shift + Control + G

You can also break apart a group of items

If you create multiple groups on the same layer each successive group will appear on top of the prior.

You can change this stacking order with the arrange command

From the menu select:
Modify | Arrange | Bring to Front
Hotkey: Control + Shift + Up

Modify |Arrange | Bring forward
Control + Up

Modify |Arrange |Send Backward
Control + Down

Modify |Arrange |Send to Back
Control + Shift + Down

You can edit items in a group by double clicking the group