you can only install one curve at the time...
Image Processing -> tone comp -> user defined curve... edit or load the curve you want to use... and its installed... need a new or different curve... connect and do these steps again...
I have a Nikon D100, tried some things with the custom curves and ditched them now... I don't need custom curves, just Nikon Capture Editor... and a Kodak Gray & Colorscale for calibrating the irst image and batch the rest accordingly... Since I work in my studio most of the times and shoot in RAW...