Starting with OS X 10.11 (El Capitan), the Spotlight search box was no longer anchored to the menu bar. Instead, it became a floating box you could move around. While this is incredibly useful, I couldn't figure out how to get the box back to center, so I did what any normal person would do: I asked the Twitterverse … and as hoped, the Twitterverse came through:
@rgriff click and hold on the spotlight icon in the menubar until it recenters
— David Halter (@elasticthreads) November 4, 2015
It really is that simple—just click-and-hold on Spotlight's menu bar icon to recenter the search box. And now, a gratuitous video (because I need all the practice I can get with screen recordings!).
Hooray for simple solutions, boo for Apple hiding them from easy discovery: The built-in help references the ability to move the box, but not how to move it back.