when I stack some splitters/mergers in front of a big container, I have to create one splitter/merger in front of the bottom input/output, then a useless splitter stacked on it, then a splitter/merger stacked on it for the top input/output of the container.
So there is a useless splitter in the middle. Often I erase it but a flying splitter/merger looks weird.
My suggestion is to create a only decorative element to stack between two splitter/mergers. It would be a kind of cylinder.