Selection Sets are a new Shortcut type. They are located in the Shortcut Area, just below Fixture Groups.
In essence, Selection Sets are for objects as Fixture Groups are for Fixtures. The Selection Sets apply to any and all drawn objects and those inserted from the Library; they can include Groups as well as Truss (along with Assembled truss). They are NOT the same as Groups, however, because they simply save which particular objects are selected, and the order in which they are selected. And multiple selection sets can be created on an object. For example, selecting Left to Right in one Selection set, and Right to Left in another selection set will deliver different results.
Selection Sets offer a few benefits. They are a great way to select Light Emitting (LE) objects in Design (or Live) by any means other than clicking on them (in Wireframe or Shaded View). Also, if you must repeat a complex selection on many objects, and order matters, Selection Sets offers a new solution.