You could make a waypoint to your own loc, but it'd be useless like I said (you're already there). There's no way to dynamically get the loc of a mob/target. And like Accredo said, the distance to your target/implied target is already built into the UI now in the target and implied target window. To see it you just have to turn it on, it's in the options (I want to say it's under UI > Name & Chat Bubble, because they keep thinking that's the target window even when it's not)
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