@User, Shift click is used to add more elements without clearing the selection. Control key while dragging with button pressed is used to select endpoints of objects (wires, lines, polygons rectangles etc) for a stretch operation Alt-click is used to unselect specific objects without clearing the selection. I think right button with shift or control can be used. Right button with no modifier keys brings up the edit attribute window. If you want i can move the 2 commands to use right mouse button click with shift /control.