Thanks!
I personally discovered a workaround until then by making a icon and then using the z/line tool to point to it with a sub-page that's off of the map card, and then if I click the map it just gives me the arrows.
It makes me wish that I could draw arrows to arbitrary places without them needing to connect to something, like pointing on my map would be awesome. It's a shame you can't restyle the lines to be less large/obtrusive for this sort of thing, though.