I need to add more points to the scale graph of my sweep nurbs object, but I can't figure out how to do it!

I know it has to be ridiculously easy, but I just can't find out how. I did it on accident a few hours ago, but I forgot what I did. I'm pretty sure I just clicked around a lot and it eventually showed up, but then I saved my project and decided to continue my work now, and I'm not having the same luck with random clicking again.

Could anyone tell me how I can add another point to the graph, where the red arrow indicates for example?