I just found that if I create the ‘nvram’ directory here (and allow user pi to write to it)
Then when playing Mame games (with mame4all-pi) the service menu (accessed with F2) will save settings here. Useful with things like flipping the screen and setting difficulty. To save the service menu you just press F2 again.
RetroPie help guides --> https://goo.gl/Yfy8kj
Please read this before asking for help --> http://goo.gl/eLErnl