By that I mean is there a command I could type into the terminal then click on a window behind, and It is scrolled up / down, and then turn this into a custom shortcut?
xdotool key Next or xdotool key Page_Down is not what I want, I'm looking for one that is metaphorically 'deeper' in the way Linux / general OSs works.
I know how to use xdotool, but I don't want to use it. I want to know the command that is executed when that button is pressed, XDO words as an emulator essentially.