Add href to tag in nav menu for mobile

This is really a problem i think you should solve with javascript if you are looking to solve it with code. I would suggest that you could probably use the wp_is_mobile to add a class to your HTML tag

If that class exists on your html tag run some JS that binds to all the menu items in question’s clicks using something like $(‘.CUSTOM-CLASS-FOR-MENU-ITEM’).click(e){ e.preventDefault();} and then the links on those menu items will do nothing.

although I think a much better simple solution, would be to add Custom link Items where the link is just a # mark which will do nothing as well but allow you to :focus it, :hover it etc. You already have two separate menu locations declared in wordpress why not build two different menus and replace that About menu Item with a custom link item and then there is no need for javascript whatsoever.