There really isn't any documentation on how to edit the quad curves (although a few people have developed their own methods for doing it—myself included). You can open the .quad file in any text editor, and then cut and paste from there. I wrote a post a long time ago about how to remap ink curves to different positions, but editing the shape of the curve is another story. Here is a link to that first post on the subject: Quad Tone Rip .quad Files
But like I said, I've done quite a bit of work figuring out how to open, correct, and export a new .quad file using spreadsheets. Roy has built a similar feature into the new version of QTR (2.7.6-2.7.7) that will relinearize the quad curves when dropping the original curve and a measurement file onto the linearize-quad app. My approach is different in that I can map the ink curves to any shape density curve I want (rather than just making a straight line), so it it more versatile and less error prone than the QTR version. The actual formulas are too involved to get into here, and it took me several months of testing and refining to get it to work the way I wanted. I do offer this as a service through my site if you are interested it just getting something working (if the QTR app doesn't do what you want).
Hope that helps,
Richard Boutwell