Can I set a default value of a feild depending on other fields?

Conditional input for that field does not work, as I hope the users can change the field if necessary.

It is the "Your Preferred Name Tag" field in the form I am working on.  I hope to set the default field with the full name provided.

Hello cherrihsu,

I am not sure if I have understood your requirement correctly. 

Do you want to populate your "Your Preferred Name Tag" field with the input value of "Full name" field. Is that correct?

You can take advantage of our "Update a form field value" condition feature to achieve your requirement. The following guide should help you :  http://www.jotform.com/help/286-How-to-Populate-Field-with-a-Value-from-another-Field

Please check the screenshot below and see if this is what you wanted to achieve:

Why I am confused is because of your statement "Conditional input for that field does not work, as I hope the users can change the field if necessary."

Do you mean to say that the above condition which I have explained above will not work? Please explain the issue you are having and we will surely help you.

We will wait for your response.

Thank you!