Popovers and lists that overflow should be scrollable with middle-click

Right now some popovers are filled with content and often overflow ('overlays' most notably), when this happens a little arrow is displayed at the bottom and one can scroll the popover to show overflowing content. However one cannot use middle-click to do the same, whereas this middle-click scrolling is valid all around Blender UI (3DView, 2DViews, regions...). I am using a tablet which makes scrolling difficult (there is no scroll wheel on the tablet pen), so I would love being able to middle-click scroll a popover or an overflowing list.