You can display a subVI as icons or as an expandable node. Expandable nodes appear as icons surrounded by a colored field. Expanded nodes of SubVIs appear with a yellow field. Use icons if you want to conserve space on the block diagram. Use expandable nodes to make wiring easier and to aid in documenting block diagrams. By default, subVIs appear as icons on the block diagram. To display a subVI as an expandable node, right-click the subVI and remove the checkmark next to the View As Icon shortcut menu item. Figure 3.10 shows the expandable node of the trigonometry subVI. If you display a subVI as an expandable node, you cannot display the terminals for that node and you cannot enable database access for that node.
When you resize an expandable subVI, the input and output terminals of the subVI appear below the icon. Optional terminals appear with gray backgrounds. Recommended or required input or output terminals you do not display appear as input or output arrows in the colored field that surrounds the subVI icon. If you wire to an optional terminal when the subVI is expanded, then resize the subVI so the optional terminal no longer appears in the expanded field, the optional terminal appears as an input or output arrow in the colored field. However, if you unwire the optional terminal, the input or output arrow does not appear.
By default, inputs appear above outputs when you expand the subVI. Right-click a terminal in the expandable field and select Select Input/Output from the shortcut menu to select an input or output to display. A line divides inputs from outputs in the shortcut menu. Labels for expandable subVIs appear in the colored field that surrounds the icon. To resize the expandable node so that it accommodates the name of each terminal on a single line in the expandable field, right-click the subVI and select Size to Text from the shortcut menu.