Besides inserting fields that belong to the post, you can add any other fields to Toolset forms. Non-post fields can serve for anything that you need, which doesn’t go into the database with the post.
In the form editor, click Generic Fields to expand the list of available fields.
You can choose from different field types. After placing in on a From you can set the field’s options by expanding the field options.
The generic fields that you add to the form are not part of the post, so Forms will not process them automatically. You are free to use generic fields for whatever your application requires. Your processing should go into PHP code and run on Forms hooks.
Visit our Automated Email Notifications with Forms guide to see an example of sending an automatic email notification to a user specified in a generic field.