Hold B to reset all joints to last modification
Sometimes I've fallen into such a bad position when struggling to make my next move that I need to go back to my last joint configuration.
This may be confusing, but let's say on Turn 1 I contract right pec and raise right hip. On turn 2, I mess with too much and I want to reset it, but I only have a few seconds left on the clock and I can't hold C and redo that too fast.
By holding B, I'l return to contracting right pec and raising right hip.