This idea has been merged into another idea. To comment or vote on this idea, please visit WEBFLOW-I-648 Add more features to the Navbar element.
The navigation/navbar should get a little button in the style section to toggle/switch between a hoizontal and a vertical mode/state.
Maybe there are also different ways to implement this, but basically the goal would be to make a vertical Navbar as easy to use (or to start with) as the default horizontal one.