Thanks for posting in! We apologized if you were not able to get a suitable response to address your issue. Please hear me out how responsiveness works in the builder. From a users perspective, one might think that building something in the builder like a logo and the inline menu items magically turns into a logo and a hamburger icon in smaller screens. Behind that, there is actually 3 elements. The logo, the inline menu items and the hamburger icon. The two elements were hidden in specific screen sizes because in reality, an inline menu items will not look good when viewed in a smaller screen.
In your case, I would say that your custom header will need two bars. One bar will be designed for the desktops screens and the second bar will be for smaller screens. You may even use only bar and just hide/show elements for different screen sizes using the "Hide During Breakpoints" option. To fully understand how this option works, please check out this thread:
And by the way, I'd like to point out that in most cases, Pro theme has been misunderstood as a buggy and a very difficult to dealt with. They tend to forget that Pro theme is highly recommended only to intermediate and advanced users like designers and developers. Because it needs to have a full understanding of how builder layout containers works so that you can easily get you way around in building anything you like. For starters, you can always check out our knowledge base to know more about the tips and tricks in Pro theme.
Hope this helps.