Sometimes when your dealing with a lot of lighting in one small spot on a plot, its easy to accidentally click other lights. If you can lock some of them in place, it'll prevent from having to deselct them and you can't accidentally move them.
If all your Layers (Lights, Gangs, Pixelmaps...) are disabled in the Plot Toolbar, you can only select fixtures in the Plot, but you can not move or edit them in the plot.
