For the OP:
If you are sitting at a campsite with full hook-ups and staying for any length of time, tying all the outlets into a single hose with Y's is the way to go.
Otherwise (sitting at the camp site), you need to make sure you have enough hose to reach the farthest outlet to the campground sewer pipe and then simply move the hose from outlet to outlet.
If dumping at a dump station, and your outlets are a distance apart, about the only option is to dump the first one, move the trailer, then dump the second one. Considering mine are fairly close to each other, I move the hose from one to the other. I only use the Y set-up in the photo above when parked for more than a couple days.
You do have the option to experiment with a more permanent plumbing install on your camper and tie them all together. If you do, you need to consider how much of that pipe hangs below your trailer frame, and don't go lower than the top of your axles to you have some sense of assurance nothing will get knocked off when traveling, especially if you experience drives and parking lots with excessive dips and hills. That's the only risk I see in adding extra pipes, unless you can get it all inside the width of your trailer frame.
Either way, good luck.
