Hidden input helps to save some information to the database after form submission without any input from the submitter side. It can be placed only inside the Form Container.

Hidden Input default state

After adding, the Hidden Input can be bound via the Data tab. The field for mapping can be selected among the Collection Container’s object fields ( not from the Form Container’s object fields).

Once the form is submitted, the data from the selected field via the Hidden Input will be added to the newly created record.