I only found out about the design tool when I downloaded the invisible magisplay tray and the OMSP's. It's MUCH easier to place your sims on the tray and OMSP's (or whatever else you're placing) put them where you want them, and then use the design tool to make the tray and OMSP invisible. HOOBOY it has saved me many a headache! (There's nothing worse than fishing around for invisible things to grab and position, know what I mean?)