*Note, what I mean is that it seems like the way I linked it caused the line to go over most part of the earth and thus the line would exist even when one is trying to zoom into African coast at that altitude. How should it be changed to make it display correctly while making it navigationally work?
I think the way for the ferry line is mapped OK, since it is split at the -180/180 longitude. The link shows the bounding box of your changeset, and that contains points on both sides of that line, thus is stretches over planet and looks like single way.
So, reg. the renderer everything should be okay. BUT reg. routing you may have problems because the ferry is connected to a man_made=pier
without a highway (both ends). I suggest to map the pier as a closed way and extend the ways with highway=unclassified to the amenity=ferry_terminal nodes.
When I made the thread, I was using a single way to connect both ends and thus it appeared to span across the entire earth at the time. I have subsequently split the ferry route to two half in Eastern/Western hemisphere and then connect them together by using a relation and then put the pier node onto a node on the way=pier way and then connect the way=pier to the island’s road.