Save button stays disabled in WordPress theme customizer

Hello fellow Stackoverflowers, I’m having a problem with WordPress.

I have added a custom section to an existing theme so that it shows up in the theme customization page (customize.php). The problem I am having is that I don’t know how to notify wordpress when changes are made in my custom control, In other words when I change the order of the items in my sortable list I want the save button to be enabled (as for now it stays disabled). I guess I am missing something in my code because it should do it in automatic? I read the official documentation but still I don’t understand how to ‘link’ my custom control (which has some javascript behind but in the end just a list)

Here is some sample code:

$wp_customize->add_section('my_section', 
    array(
        'title' => 'My title',
        'description' => 'My description',
        'priority' => 201
    )
);

$wp_customize->add_setting(
    'my_setting',
    array(
        'default' => '',
        'type' => 'option',
        'transport' => 'postMessage'
    )
);

$wp_customize->add_control(
    new My_Control(
        $wp_customize,
        'my_control',
        array(
            'label'    => 'My label',
            'settings' => 'my_setting',
            'section'  => 'my_section'
        )
    )
);

Note that My_Control is a class which enqueues additional JS/CSS files and renders my sortable list (extends from WP_Customize_Control). I am storing my model in an array rather than using multiple settings; I add my model to the page using the wp_localize_script function.