Joe is 100% right here. The Spectrum display, CW, Signal strength, and any other graphs have to be changed programmatically. And it gets real ugly, really fast. Load up one of the screens in the Nextion editor and go look at the "timer" tabs and try to sort them out. You have to figure out where the top and bottom of the graph are located on the display, scale the data to fit into that location, draw one color for the signal, one for a peak (in some case) and black for the other ones to blank things out (and I think you do this top down). And then, if you have any vertical red lines like a couple of the display, you need to draw them too.
Not trying to dissuade you here. Very doable. "Just Math". But plan on spending 5+ hours per graph....