The Shift key is very useful for extending selections. If you think about it, it functions in DAW programs the same way as it does in word processors, or as it does in most programs. If you have already made a selection, holding down Shift and clicking on another item will add the new item to the selection, and also any items between the original item and the new item. This works for words on page in a word processor, for items in a list, such as the clip list, or for clips on a timeline. You can extend a selection on a timeline, by Shift clicking on blank space after or before your original selection. This will extend the selection by the amount of time between where you clicked and the original selection.
Try it out. There are many situations in which the Shift key will allow you to extend your selection. This can save you time, and improve your workflow.