What is JotForm?
JotForm is a free online form builder which helps you create online forms without writing a single line of code. No sign-up required.
At JotForm, we want to make sure that you’re getting the online form builder help that you need. Our friendly customer support team is available 24/7.
We believe that if one user has a question, there could be more users who may have the same question. This is why many of our support forum threads are public and available to be searched and viewed. If you’d like help immediately, feel free to search for a similar question, or submit your question or concern.
You may like to take a look at our "User Contributed Dropdown" widget and that should help you achieve your requirement. In this widget, user will be able to add his own option in a dropdown field. I believe this is what you were trying to achieve.
Hope this helps.
Do get back to us if you have any questions.