qed was also a line editor but pre-dated and inspired ed, so that's pico to nano or ed to ex again, just even further back in time.

sed and grep grew out of commands within ed (or equivalent) so I guess you could say they're each kind of a knight's move two to the side and once backward from the direction of ex to vi. Backwards because they're simpler, but two to the side because they're not interactive.

As to what would be "backward but one to the side" in that analogy, that'd be something like a tool that asked questions about every line in a file and made changes accordingly. I don't think there's any such standard tool, but I can think of at least a couple of ways to write one.