omnicore flexpendant button

we have a brand new Omnicore C90XT that we're setting up. pretty much done and I'm going through everything, dotting t's crossing i's, and I noticed a button that I had never seen or used before. If the screen is the front of the teach pendant it's on the top seemingly meant to be pushed by your thumb as you hold the dead man switch. what is this button for? I've done some research looking for an IPB for the pendant or a button layout but I can't find anything about it.