If you want different Custom Registration Fields to appear on the same level Pro-Form, you will need to create your own custom Pro-Form templates (see: Is it possible to modify s2Member® Pro Form templates?).
You will then need to use the template=”” shortcode attribute in your Pro-Form shortcode to specify the custom template you want to use for that specific Pro-Form. See the following description taken from Dashboard -› s2Member® -› PayPal® Pro Forms -› Shortcode Attributes (Explained):
template=”” 100% optional. This can be a custom template file that exists inside your WordPress® theme directory. For example: template=”checkout.php”.
Of course you’ll still need to create the Custom Registration fields in Dashboard -› s2Member® -› General Options -› Registration/Profile Fields.
After you create the Custom Registration Fields, you’ll need to build a custom Pro-Form template so that you can specify it in your Pro-Form shortcode.
The easiest way to build a custom Pro-Form template would be to simply display a Pro-Form on a page with all the Custom Registration Fields visible, then view the HTML source for that page and copy the HTML for all the custom fields.
The default Pro-Form template file that you use as your starting template for your custom Pro-Form template won’t have any of your Custom Registration Fields in there because they’re dynamically added by s2Member when the Pro-Form loads.
So, you’ll need to add all that Custom Field HTML code into your custom template file manually. It’s easiest to just copy/paste the generated code instead of trying to retype it all. After copying the generated Custom Field HTML code, you’ll need to paste it into your custom Pro-Form template in the relevant spot, and then remove any Custom Fields that you don’t want to show up in this specific custom Pro-Form Template.