When placing a belt on a constructor on one end then you can connect a belt on the other end, the option of a merger/splitter would automatically show up. For example I place the input to a constructor then aim at a belt and it shows a splitter you can slide back and forth, then place. This would work just like when you place a splitter on a belt now. The starting belt direction determines if it is a splitter or merger. Right now most of my time is spent on placement of splitters and mergers on a bus line, then connecting everything up. This would cut down on setup time greatly.