If you look next to the dropdown menu for Picture Control (monochrome, Vivid, etc) there's a Launch Utility button. This allows you to create custom Picture Control settings.
THIS include a curves adjustment, if you click around a bit in it. It's a really really badly designed bit of user interface, but there it is.
Unfortunately, I don't see how to do a curves adjustment on a picture by picture basis. You have to define a new named Picture Control, with a curve, and then apply that to your picture. Which sucks. But it does kinda work..