Microsoft is experimenting with taking Search out of Cortana and making it more Mac-like in the newest Windows 10 build.
But that's overkill when you're just looking for a file.
In Windows 10 Build 17040 there's now a cleaner search UI – although Microsoft doesn't list it as one of the new features. And you'll need to make a registry hack to enable it.
Once enabled, the Search UI becomes a box in the middle of the screen, like the macOS Spotlight box.
Windows Central has pictures and instructions.
It's worth stressing that there's no guarantee this new UI is going to be implemented in release code as the default behaviour. And we even hesitate before urging you to write in and ask that Microsoft to do the sensible thing and make it so.
By the time your feedback has been processed through SatNad's amazing Cognitive Engines, it'll do the opposite. ®