I've just pushed a real-time apropos for replant. I think it's quite good, run :ReplantApropos and fzf will pop up with every symbol available. You can open the source of it, or show the documentation for it in a buffer. I think I missed a few edge-cases, so I welcome bug reports (as I always do). This would make a good alternative to grep/fzf for doing the same kind of thing.