[netmare]

An X-Mouse mode was available since at least Win98SE [1]. It was hidden and you had to enable it in the Registry [2], typically via Tweak UI.

That mode would move the input focus without actually clicking on another window. You could see the caption bars change color accordingly, but the "temporarily" focused window could be set to either stay in it's original z-order or moved to the top.

Windows 10 uses a different method: it doesn't change the focus and only sends mouse scrolling events to the target window. That's less powerful, but probably more intuitive for us non-*nix users.

[1]: https://stackoverflow.com/questions/70599589/how-do-i-turn-o...

[2]: https://superuser.com/a/19643