I've seen where dog owners have put up a raised line (like a clothes line) and attached the leashes to that. It still posed some tangle problems but appeared to be better than the alternative.
Yea, that's what we did. One line for each dog. The problem was on this particular site, there was only one good tree to attach all three lines. So as the dogs got together at that end, they'd tangle with each other. And they'd wrap themselves around the tree or the tie down points at the other ends of the lines. Next time, we'll try for a site that has tie down points that will keep the dogs well away from each other. I will also work something onto the lines that will stop their travel before they can reach the tie down points and begin wrapping themselves up there.