Choice Action Items can contain nested items of the same ChoiceActionItem type. So, each of nested item can contain items as well. This property provides access to the nested items collection. The most convenient way to specify this property is to use the ChoiceActionItem Collection Editor. To invoke this editor, use the ellipsis button of the Choice Action's Items property in the Properties window. In this editor, you can add items to the Action. To add items to a selected Action item, use the ellipsis button of the item's Items property.