I found this infor here: BMW ConnectedDrive: Rear View Camera

It clearly shows a hitch symbol as the last option in the vertical menu on the left of the screen. When I connected the trailer what I found is the same symbol, only much bigger somewhere on the right hand side of the screen, It's not clickable though. BTW, I had an Execuhitch installed, I'm really happy with the way it looks on my car, no cutouts, very clean, I haven't towed yet.