In properly designed bars this is either a default or a configurable option. Moving your mouse to a far away bar and holding shift are more expensive actions than pressing PgDn (or a shortcut), so the action can't be just a page, it has to be something more valuable, harder to replicate (the even smaller arrows at the top/bottom are even worse)
That's a counter against another common sin of UI design that's stuck in the past, another superficially appealing idea that requires users hunting for tiny lines for common operations. That one should be fixed instead of making the scroll bar worse. (they even have that whole dedicated "windows" button that doesn't properly manage... windows)
Besides, lack of proper universal undo (that can undo selection/position changes, including windows) is yet another desktop UI design failure. Similarly to what you've noted, the solution to which is yet again fixing that instead of breaking useful functionality in other elements. So maybe it should be Win+Z to undo window resizing/moving?
A) Both hands on the keyboard, making it easy to reach both the Win key and the arrow keys at the same time to snap your windows.
or
B) One hand on the keyboard and one hand on the mouse, making window snapping instant with the mouse.
But I forgot that this is HN, so a significant proportion of readers also use their computers with both hands on the mouse, or no hands and one foot each for the keyboard and for the mouse.
Edit: Sorry for being sarcastic.
> A) Both hands on the keyboard, making it easy to reach both the Win key and the arrow keys at the same time to snap your windows.
It might be "easy" to reach arrow keys, but it's even easier and faster not having to do that
> B) making window snapping instant with the mouse
Your left window slightly overlaps the right one. You want to resize it by reducing its width by ~5% and its height by ~9% to avoid that Name your "instant" list of mouse actions to achieve that.
Then they can also jump back and forth effortlessly between two places in a document.
The only somewhat similar function I've seen is on Kindle when you jump between footnotes or chapters, and they provide a very convenient interface for jumping back, but buttons instead of scroll bars.