On Windows, pressing the mouse wheel drops an anchor and the page scrolls toward the pointer, hands off. No Mac app does this, and macOS has no setting for it; the middle button is just a third button.
What it does do:
- In browsers, middle-clicking a link opens it in a new tab, and middle-clicking a tab closes it, as on Windows.
- Elsewhere, most apps ignore it. Some use it for panning, such as map and design apps.
Trackpads have no middle click at all by default. Long pages are meant to be scrolled with two fingers, and a flick keeps scrolling with momentum, which covers some of what autoscroll did. Free tools add a three-finger tap as a middle click.