This option unselects all network items. This is useful to make sure all items have been unselected after a cut, copy, or Arrange menu operation. There are three choices under this option:
Current Set (Shortcut keystroke: Ctrl-A) - Unselects all items in the current Select Set (see explanation below).
All Sets - Unselects all items in all Select Sets (see explanation below).
Except Last (Shortcut keystroke: Ctrl-E) - Unselects all items in the current Select Set (see explanation below) except the last item that was selected.