Q: 4K Works on MBP, But How to Change ???

I recall awhile ago when I could get into the Display control panel and select multiple resolutions for external monitors.

I have tried to hook up a 4K monitor to my MBP retina, and it outputs maximum resolution all the time to the external monitor, making everything far too small.  Nice realestate, beautiful picture, but overkill.

Also, if I've hooked up an external monitor, there no longer seems to be a way to choose a different resolution for the second screen.  This seems to me like a step backward.

How do I get this flexibility back, so I can change resolution of the external monitor separately from the resolution of my retina screen?

Am I mis-remembering this?  Is this not possible with Retina anymore?