Edited to make into a toggleable (if that's even a word) addon
Code:
SLASH_HIDEARROW1 = "/hidearrow";
SLASH_HIDEARROW2 = "/ha";
SlashCmdList["HIDEARROW"] = function(msg)
if WorldMapUnitPositionFrame:GetAlpha() == 0 then
WorldMapUnitPositionFrame:SetAlpha(1)
else
WorldMapUnitPositionFrame:SetAlpha(0)
end
end