How to apply sub-categories to payment field in v4 builder?

This feed doesnt apply with the updated 4.0 designer. The instructions are no longer applicable. Can I have an update please.

This is still applicable, but in the new builder you cannot get the option to view the source code of your form, what you could do is to preview it and right click on the free product that will serve as sub-label, then copy the input number as explained on the guide. 

Example: 

Also, the way how you add products has changed in the new builder, here's how the wizard looks now: 

The CSS code is the same as explained in the guide, here's also a sample form about it: https://form.jotform.com/53497306922966 

If you have any question, let us know.