[sgt]

I do the same thing, but the extent of my "legend" is simply the following:

"->" (random points)

"o" (random points)

"[ ]" (thing I need to do)

"[/]" (thing I need to do, in progress)

"[?]" (I don't know what to do, might revisit)

"[-]" (Not going to do this one, maybe it became redundant)

This helps me a lot to line up my thoughts and know where I am. However, I really like the legend as described by OP, so I might change mine towards that approach.