This sidedown overlay theme includes a widget which displays when you click the search icon on secondary nav menu.
Here’s the demo video:
The overlay effect has been coded into a fresh copy of the Genesis Sample child theme by StudioPress.
The theme includes a custom widget area which you simply populate with the native search widget included in all WordPress installations.
Credit to Codrops for the original code which has been modified to work in WordPress.
Simply download the child theme below and install after the Genesis theme framework: