I have upgraded to Jenkins ver. 1.596, which is latest and greatest. I observe that,

When you change the job config and try to save, You won’t see Save / Apply button. (please see screenshot)

The real problem is Save / Apply button is hidden below the Jenkins footer overlay, Even when you try to scroll bottom most you won’t see the buttons.

Workaround: In browser, Go to full screen mode (f11), You will see the buttons to Save / Apply.
Apparently, this bug looks like a HTML layout issue.

I have tried in multiple browsers and see the same issue.