+=1 in Time Value Box will Slide the key 1 Frame Forward. And here is Shelf Icon Code for that:
keyframe -animation keys -option over -relative -timeChange (0 + 1) ;
If we type *=-1 in Keyframe Value Box it will return Reverse/Opposite Keyframe Value.
I don’t know scripting but I tried using different flags, formulas…no output.
Do anyone knows command line version? So I can put it on Shelf.