Hello,

Unfortunately, there is no easy way to reduce the number of checkout steps, otherwise it would have been done already by default, you will need to do some custom development. You will need to create a custom checkout step and then combine the default checkout step controls. All of the code files you will need can be found in the following location: "~\CMSModules\Ecommerce\Controls\ShoppingCart\".

I'm afraid there is not a whole lot of documentation for this approach, but here this article on creating custom checkout step should get you started.

Regards,
Josef Dvorak