Item groups can be used to specify which items qualify for a discount—provided by a gift, punch card, or club deal.
If you'd like to include different items in a discount (even if it's only adding or removing certain items from the item group), you need to create a new group for the desired items. .
From Campaign Center > Gifts > Choose a certain Gift> Terms> Add Condition> Select Item> Saved Groups> click on the Edit pencil icon, you can create a new item group from the Scenario tab: