Filter testimonials_widget_sections and testimonials_widget_settings examples.

testimonials_widget_options.php

add_filter( 'testimonials_widget_sections', 'sections' );
add_filter( 'testimonials_widget_settings', 'settings' );
public function sections( $sections ) {
	$sections[ 'premium' ] = __( 'Premium', 'testimonials-widget-premium' );

	return $sections;
}
public function settings( $settings ) {
	$settings['premium_expand_begin'] = array(
			'section' => 'premium',
			'desc' => __( 'Premium Options', 'testimonials-widget-premium' ),
			'type' => 'expand_begin',
			);

	$settings['clearcache'] = array(
			'section' => 'premium',
			'title' => __( 'Clear Cache?', 'testimonials-widget-premium' ),
			'type' => 'checkbox',
			'class' => 'warning', // Custom class for CSS
			'desc' => __( 'Check this box to clear the testimonials cache', 'testimonials-widget-premium' ),
			'widget' => 0,
			);

	$settings['no_cache'] = array(
			'section' => 'premium',
			'title' => __( 'Disable Cache?', 'testimonials-widget-premium' ),
			'type' => 'checkbox',
			);

	$settings['maximum_length'] = array(
			'section' => 'premium',
			'title' => __( 'Maximum Length', 'testimonials-widget-premium' ),
			'desc' => __( 'Maximum number of allowed characters in testimonial', 'testimonials-widget-premium' ),
			'validate' => 'min1',
			);

	$args               = array(
			'public' => true,
			);
	$post_types         = get_post_types( $args, 'objects' );
	self::$post_types[] = Testimonials_Widget::PT;
	$choices            = array(
			Testimonials_Widget::PT => __( 'Testimonials Widget', 'testimonials-widget-premium' ),
			);

	foreach ( $post_types as $type => $data ) {
		if ( 'attachment' == $type )
			continue;

		self::$post_types[] = $type;
		$choices[ $type ]   = $data->labels->name;
	}

	$settings['post_type'] = array(
			'section' => 'premium',
			'title' => __( 'Alternate Testimonial Post Type?', 'testimonials-widget-premium' ),
			'desc' => __( 'Set this to use Posts, Posts or another custom post type for testimonials', 'testimonials-widget-premium' ),
			'type' => 'select',
			'choices' => $choices,
			'std' => Testimonials_Widget::PT,
			);

	$settings['premium_expand_end'] = array(
			'section' => 'premium',
			'type' => 'expand_end',
			);

	return $settings;
}