Hi,
One way I found to display a set of questions in a catalog item in that staged manner you are looking for was to create variable sets for each 'section' and put all the questions I want answered in that stage, or variable set. In regard to your summary section, I would recommend removing that entirely. Once an item is submitted (clicking that Submit button), if you have not changed the redirect in the SC Catalog Item OOTB widget, then you should be automatically brought to a new page, I believe it is called sc_request, and it will render for the users a summary of the Item they just submitted, kind of making your last 'stage' redundant. If you don't like the sc_request summary page, then you can Clone the SC Catalog Item OOTB widget and change the handleRedirect() function. Question about the other part of your inquiry: Is the Child Stepper intended to simply add more fields to the form if 'Advanced' is toggled? Or does every user have to input values in the 'Advanced' stage. If the former, I'd recommend a different approach than making it a stepper, since you already have one. You could make that Child Stepper a Boolean check box variable and simply hide variables that are intended to be answered when 'Advanced' is checked, with Catalog Client scripts, or configuration in the 'Advanced' variable forms. Lastly, how are you cloning the OOTB SC Catalog Item widget? It may be that you need to edit the page configuration to point or use your cloned SC Catalog Item, rather than the OOTB one, you can do that in SP Config under Pages, or the Designer within SP Config. For keeping it really simple, clone the SC Catalog Item Page, don't make any changes, go to the Page Designer in SP Config, and change the widget instance in that page to use your cloned widget.
