Somebody certainly did... It is an efficient way to replace a part of the clips on the timeline with another clip, precisely where and how long you want to have it. The tip works the same in PREL 7.0, only the second window (after having selected Overlay) does not appear. Set the In Point in the Preview Monitor, and that's where your new clip will start at the timeline. Great tip!
BTW: Once this In-Out-Clip-Bar has been set, you can move the left and right edges (the History Panel names them Sequence In and Sequence Out Points) and slide the bar itself: in the middle there's the same little icon the Work Area Bar also has.