Op is asking for a progressive gradient that affects more than one button (judging by the top image). And how would you define which button is at the arbitrary top/bottom if it’s a scrollbox child? We also do not know how the scrolling is supposed to work? Is it fluid, is it a set amount, is the amount equal to the button’s height? If you use the mouse wheel, you get 32 pixels as default (at my end, this may depend on the system settings, I guess), but if you drag the slider, you can get a pixel perfect value.
There used to be a way to cast a widget to a slot to get it’s relative location in a scrollbox but I honestly can’t reproduce it anymore.