Code:
/run local c,p,t,m=C_Map,"player","target" m=c.GetBestMapForUnit(p)c.SetUserWaypoint({position=c.GetPlayerMapPosition(m,p),uiMapID=m})SendChatMessage("%t "..floor((UnitHealth(t)/UnitHealthMax(t))*100).."% "..c.GetUserWaypointHyperlink(),"CHANNEL",nil,1)
This macro will create a waypoint at your location and share it, along with your target's name and health percentage, to the General channel. Delete SendChatMessage and everything after it if you just want the waypoint creation.