I looked for this one for quite a while. I thought it was part of Offset = or hidden somewhere in Trim. It just turned out to be lost in the = conversion to object/action~pick the object and the functionality = suddenly appears. And it's even called Extend. The trick is turning a = surface edge into the fuzzy red worm. As soon as that happens, you go to = the Edit menu and Extend isn't greyed out anymore. Click Extend and you = get some default extension and extend options. The drag handle is nice = though it seems oblivious to scale. Some Merge>Intersects are now = possible that weren't before being able to make "sloppy", overlapping = surfaces.