The Name Group function allows you to rename an existing group.
Using the Function:
Select Name from the Tools>Group submenu.
You are then prompted to enter the existing group name that you intend to change.
If the name you provide is not recognized, an error dialog will appear.
If the name you provide is recognized, you will be prompted to enter a new name for the group. The group will then be renamed (given that its original name was recognized, and given that you were prompted to rename it).