It is not a "loop intersector line". It has nothing to do with loops or intersections. It is the separator between frames of the seqeuence. And its not a stacked sequence, but a flat sequence.
Right click on your sequence frame and select "add frame before". It will add an empty frame before the one you have. If you already have code on your block diagram that you want to put into that frame, you will have to drag and drop it in, and reconnect any wires and tunnels.
