You can Add and delete of the cargo which exists now. This means change of the number. You cannot Add the cargo of a new kind with a Cube Magic viewer. When you add a new kind cargo, you adds a new kind cargo by the CubeMagic packing editor and CubeMagic engine calculates arrangement, look at it with a viewer.

How to delete the selected cargo, select menu [edit]-[cut] and [delete].

The [cut] portion can be [paste]. If a cargo of a certain container is [cut] off and it [pastes] on other containers, it will become movement between containers.

How to add a cargo, you select cargo, chooses [edit]-[copy] of a menu and [paste], or chose a cargo from [display]-[cargo list] of a menu, and click a [add cargo].