[Q] How to not replace active window when a loading game launches?

I remember being able to clic in whatever window a few seconds after the last second sound effect in the champion selection screen and it would stick to that window as the over-the-top and active window. It had to be in borderless mode but it worked and didn't had to Alt + Tab every single time. Was that "addressed" and fixed and is no longer possible? I liked it too much. Only thing I had to do was to touch the horn of the... I mean, a single clic away from LoL. Even in borderless it does almost the same as fullscreen (in regard to launching on top of EVERYTHING and forcing me to alt + tab).