How to create a line with nested labels or fields?

I would suggest you to please take a look at our "Dynamic Dropdowns" widget and see if that fits into your requirement. This widget will allow you to create more than one drop-down list with this widget where you can add number of child dropdowns within the related parent list. When the user selects one option in the parent list, the related child lists are displayed.

Hope this helps.

Do get back to us if you have any questions.