Complex order form presented as series of linked screens [Somewhat new to Drupal Commerce and Webform; trying my best to construct this question in a clear way]: The project involves order forms for a combination of fee-charged workshops and also a series of no-fee workshops where the person needs to make 2 choices among 6 options but must rank them by preference (in case they can't get their top choice). So there are several kinds of choices the person needs to specify. Then the form needs to collect a wide variety of info, not just basic contact info. Finally it needs to collect payment for the items requiring it. 

I already have a Webformbased structure that does all these things. (Although maybe not very efficiently.) It all exists on one page, using collapsible fieldsets to keep the initial view of the page simple and to have everything in one place. It makes sense to me, but for the new user I think it may be confusing.

I am thinking, it would be "better UX" if the various parts of this ordering process were divided into smaller chunks. I am thinking, either pages or maybe modal windows that are clearly and boldly identified as Step 1, Step 2, etc. and with the option to go back if desired. The results from each page or modal window would of course need to be compiled as part of the same order.

Is there a path to this sort of order form structure via existing modules, or is this a custom code project?
It was a lack of useful earlier search results that led to posting the question. But often the query just needs the right search term. In this case, it's exactly "multistep" or "multi-step." That finds this, which along with the ensuing discussion and comments, answers the question quite well: 
https://www.drupal.org/node/324779 

So, the capability was already there in Webforms, I just hadn't seen how to use it.