You can select multiple items with the mouse by dragging a rubber band around those items. Usually all icons become de-selected when you start dragging the rubber band. But you can prevent this by holding the ctrl button. Therefore it is possible to combine multiple select operations.

However if you shrink the rubber band by moving the mouse cursor closer to the origin of the rubber band, even only a single pixel, all items outside of the rubber band become de-selected. This behavior is unwanted.