How can I prevent new window focus from overriding cursor focus?

For instance, if I'm opening a handful of apps that take a bit of time to start up, and then start dragging windows around to set up my workspace, each time an app finishes loading or a new window is created, I'll be yanked out of my dragging and forced into focus on that window.

I need a way to prevent these windows/apps from automatically seizing focus, it's REALLY fucking annoying. Steam especially will hog focus 3 or more fucking times in its startup process. This is such a stupid default function.