Actually, no. It's not missing.
In fact, not only can you plot a lead distance, you can also position yourself at a pre-specified attack station (something that intercalc can't do).
For a simple lead distance, all you'd need to do is plot another contact 20k yds ahead of the real contact and then plot the intercept for that second contact. I've included a way to set contact vectors equal (mouseover and press the equal key) for quickly adding stuff like that.
I frequently plot submerged intercepts to attack stations that set me up for 30° AoB at 2500yds.
Remember, maneuvering boards are used IRL for solving stationing problems. ...and if it can be done on a real moboard, it can be done on MoBo. I'm just leaving work, but when I get home I'll post your example with the 20k lead.
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