When you use a mapplet in a mapping, the Designer displays the mapplet object, which contains only the input and output ports of the mapplet. However, you can expand the mapplet by clicking Mappings > Expand from the menu.
When the Designer expands the mapplet, it displays the entire mapping with the mapplet transformations. It does not display the Input and Output transformations. You can view the mapping in this expanded form, but you cannot edit it. To continue designing the mapping, click Mappings > Unexpand.