WPForms: display a form under the confirmation message with or without user entered field values.

add_action(

	'wpforms_frontend_output_success',

	static function ( $form_data, $fields, $entry_id ) {

		unset(

			$_GET['wpforms_return'],

			$_POST['wpforms']['id']

		);

		// If you want to preserve the user entered values in form fields - remove the line below.

		unset( $_POST['wpforms']['fields'] );

		// Actually render the form.

		wpforms()->frontend->output( $form_data['id'] );

	},

	42,

	3

);