How to prevent a collapsed section from being submitted?

I am trying to create a form with multiple collapsed sections. I would prefer for blank or unused collapsed section to not be submitted. Basically, can the form only harvest the populated fields on submit. Help?

You can add checkbox fields so that users can select if they wish to add another recommendation. Then you can add conditions so that if user selects checkbox only then will show the collapses:

You can also enable the hide empty fields on emails:

This way only the filled in fields will show on the email notification.

You can clone  and test the demo form:

http://form.jotformpro.com/form/51135640856960? 

Let us know if we can assist you further.