Reply to TRAKTOR 2.5 mapping command for "jump to track start"

right,
this is a question so simple and yet this ha driven me nuts trying to find the mapping command in T2.5
on the Track Decks there is the function "Jump to track start" just under the waveform on the left of the deck
which any normal traktor user will know....

some one PLLLZZZ!!! put me out of my misery

and tell me where to find the command in the controller manager...