NSEU - you'd have to enter the speed/altitude on the R side of the FMC.
Farmer - Rarely done but I have used it. The best recollection I can think of right now is when the FMC arrival fuel is much higher than planned. "What the heck is it looking at??" Check and it shows over the last fix(co-located with destination ie JFK) at cruise altitiude. Enter a speed and low altitude and it computes a more realistic ETA and fuel vs. having to spend more time selecting DEP/ARR, STAR, ILS XX, etc, etc. It's just a quick snapshot to check flight plan data vs. FMC data with minimal effort and it can be deleted or will be removed when the box is 'cleaned up' after inserting the correct STAR/runway combination later in the flight.
Honestly with 20+ yrs, and numerous a/c types and FMC versions, I can't remember if my current FMC 'unwinds' to destination altitude automatically. Something to refresh my brain cells with on my next trip.
