Popup Window to Navigation Menu like Nimblehost Site

Hello i need to do a website with a popup window reveal in navigation menu like Nimblehost Website https://www.nimblehost.com/store/mymenu/

When you click Store in navigation menu appear a popup window with other link section to website.

How can i do it? Which stacks or plugins i need it?

Thanks for your Help

There are a couple of ‘mega menu’ stacks

but I don’t know how you’d add their functionality to your theme’s menu. That’s above my paygrade.

I’m 90% certain you could achieve this with Foundation using Big White Duck’s Joey stack (http://demo.bigwhiteduck.com/Joey/offsite/MegaDropDown/) but that may be an investment in time and money that’s too far for you.

Alternatively, I’ve got a sneaking feeling I’ve seen a theme with this kind of menu built in but I can’t quite place it.

Maybe someone else can?