[Solved]Question about button mapping

[SNap92]

Hi guys,
I recently bought a controller for my mobile device and I mapped all the buttons correctly but I cant seem to find the frameskipping button (don`t know if it`s actually called that).

Could someone please tell me where I can find the option to set the frakeskip button (I`m talking about the button that`s on the left of the select button, the one with an small arrow pointing to the right).

Thanks in advance