An example of how to add widget titles using the Customizer.

customizer-widget-titles.php

// Register demo widget area.
genesis_register_sidebar( array(
	'id'          => 'demo_widget',
	'name'        => __( 'Demo Widget', 'mytheme' ),
	'description' => __( 'This is the demo widget area.', 'mytheme' ),
) );

// Hook demo widget area before site footer.
function mytheme_demo_widget_area() {

	// Get the widget title set in the Customizer.
	$title = get_theme_mod( 'demo_widget_title', 'Demo Widget Title' );

	// Display widget area and print widget title before widget content.
	genesis_widget_area( 'demo_widget', array(
		'before' => sprintf( '<div class="demo-widget"><div class="wrap"><h2>%s</h2>', $title ),
		'after'  => '</div></div>',
	) );
}
add_action( 'genesis_before_footer', 'mytheme_demo_widget_area' );

// Add Customizer section, setting and control.
function mytheme_customize_register( $wp_customize ) {
   
	// Add Customizer section.
	$wp_customize->add_section( 'widget_titles' , array(
		'title'      => __( 'Widget Titles', 'mytheme' ),
		'priority'   => 110, // Below 'Widget' section.
	) );

	// Add Customizer setting.
	$wp_customize->add_setting(
		'demo_widget_title', array(
			'default'     => 'Demo Widget Title',
    		)
	);

	// Add Customizer control.
	$wp_customize->add_control(
	    new WP_Customize_Control(
	        $wp_customize,
	        'demo_title',
	        array(
	            'label'      => __( 'Demo Widget Title', 'mytheme' ),
	            'section'    => 'widget_titles',
	            'settings'   => 'demo_widget_title'
	        )
	    )
	);
}
add_action( 'customize_register', 'mytheme_customize_register' );