Is it possible to create smaller ICONS on the block diagram? I would like one of my sub VI's Icon to be the same height as a singe array element (or upper to lower case conversition function).
Sure, you can make them smaller and even odd shapes or no border at all. In the icon editor, delete everything there and then use the pencil or rectangle tool to draw a solid box. I find it helpful to check the Show Terminals box to draw the rectangle to include the used terminals. Make sure you copy the icon to the 16 color and black and white versions.