Right now if you scroll with middle clicking it's handled similarly to grabbing the scrollbar, I find it more intuitive to have it inverted (similarly to how you'd move around when zoomed in on Gwenview) you can already do that with "invert scroll direction" but I'd like the option to invert it separately from the scroll wheel.
This seems to make sense as a wishlist item - thanks for the suggestion!
This is not doable unfortunately. The clients handle the scroll by middle clicking, we cannot change every app.