Wow, what a loaded question!
"Design" is really all in the eye of the beholder, no? I mean, some folks will look at something and proclaim it as the most moving piece of design they have ever seen while others look at the same exact thing and yawn, possibly wondering what drugs the designer was taking when it was created.
Unfortunately, with "help", we see nothing but conflict. Ask around. It's the absolute LAST place folks want to find themselves. Many think it's an admission of defeat to have to resort to using help. And many have had nothing but bad experiences with help being, well... less than helpful. So they are reluctant to use it.
It may be helpful if you were able to articulate exactly what you dislike about what RoboHelp creates and tell us how you plan on using the output. That might spawn some thoughts as to what you could do or try.
To jump in: if you use Responsive HTML5, you have great control over your output. Since that format is HTML pages with RoboHelp widgets, the sky is the limit. It will require a good proficiency in HTML and CSS, but you can do what you want. For a little less drastic, please answer Rick's question first.
With RoboHelp, you can create a web page (in the skin or in a topic) that works this way. But it will require custom css (and perhaps JS).
With RoboHelp 2015, you may be able to leverage the TOC for this as well. I have been playing around with it to create a top menu, but I don't have it working quite yet. If I can get something to work reliable, I will let you know.