I think hidden fields should be able to be used for conditional variables.
Case use: I use URL Params to identify the person submitting the form. This autofills a hidden field. If that field is empty, I want to be able to hide some parts of the survey using conditional filters.
This could also be a way to block people from accessing the form if every field was conditional upon a hidden field being set, extending only the form to people that have the correct link. For instance a name or password.
Examples:
If the hidden field password is blank because the person just went to abc.com - then the form would not show any fields, or just selected fields. This would be to separate the form from someone who just landed on abc.com
In this case, similar to the one above, a link was sent to a particular customer for identification purposes, and we would be able to ask this person specific questions we may not want to ask everyone.
“~www.abc.com?name=Joe%20Doe&service=paint”
In this scenario we would be asking our client John Doe questions about the service he received. Here we would be asking paint questions because the service he received was paint, instead of perhaps a cleaning service that we may also offer. This would help better target correct form fields and expand use.