More impositions can only be used in Extended mode.
These tabs make it easy to work with multiple impositions at the same time which can be useful if the final printed matter is printed using several different impositions. Typical example of this is printing a magazine cover (with staple binding) separately (e.g. with different paper weight, lamination etc.) from the inside of the magazine when cross-fold is used. These two impositions can be prepared at once. Automatic page assignment can be used and linked to other imposition which makes it unnecessary to count the inner pages manually. Paper thickness correction can be also bound to another imposition so that even the inner pages, printed separately, will be shifted correctly.
Double clicking a tab caption makes it possible to rename it. More impositions can be added or deleted by clicking + or X respectively. Imposition order can be changed by dragging their tabs, which is important while using automatic page assignment and while binding paper thickness correction to previous imposition.