Rudimentary/mostly broken support is now there
Having bought a new Kobo Touch last week and played around with it, I can say that it has a kind of extremely unreliable, intermittent, and fiddly endnote support on board already—it is occasionally possible to jump to endnotes by touching them, and somewhat more often possible to jump to the corresponding spot in the text by touching somewhere near the number on the endnote. I've tried to find a trick or maneuver that makes them work systematically, but no luck: it really only works a small fraction of the time, for the moment. Still, I guess this means it's in progress...? Writing Kobo support to draw their attention to this thread and ask for a reply.