I haven't seen it, but that's a good idea. Maybe something to submit as a feature request?
Admittedly, not sure how far you'll get with that - "real life" seems to have affected Subtext and it's stagnating. The code is fairly "organically grown" in there and really hard to navigate, so it's hard to get any new folks on board, which is one of the key reasons I haven't been able to contribute. I can't figure out where most anything is, and if I modify it, what will I break? (Yes, I'm ranting a little, but the point is... if it doesn't exist, it's probably up to you to implement it.)