Options to change parent link behaviour in responsive dropdown menus

This is a follow-up of https://github.com/backdrop/backdrop-issues/issues/2107, extracted from https://github.com/backdrop/backdrop-issues/issues/2367.

In a dropdown menu that responds to smaller screens/devices, when you have a parent link that you want to click on you have to essentially double-click on it - once to expand the child menu, and then again to navigate to the parent link's URL. At the same time (when clicking the parent link), the child menu disappears, so it appears to be that clicking the parent link the second time simply closes the child menu, that is until the page reloads and you're taken to the parent's URL.

I understand that this is what some people are used to having in a responsive menu, so I'd like to suggest at least having the option to change this behaviour to one of the following:

1. Clone the parent link into the child menu so that the parent link simply becomes an open/close button for the child menu and the parent's URL is accessed through the cloned link.
2. Make the parent link link only to it's URL, and leave the opening/closing of the child menu to the +/- sign on the right.