Customize Menu | Styling LESS/SCSS code formats

I was able to get SASS syntax highlighting in a code textarea in Customizer with the following:

add_action( 'customize_register', function( WP_Customize_Manager $wp_customize ) {
    $wp_customize->add_setting( 'favorite_html' );
    $control = new WP_Customize_Code_Editor_Control( $wp_customize, 'favorite_html', array(
            'label' => 'SASS',
            'code_type' => 'sass',
            'settings' => 'favorite_html',
            'section' => 'title_tagline',
    ) );
    $wp_customize->add_control( $control );
} );

via @westonruter in track.

The editor is powered by CodeMirror, since 4.9, so if you’re looking for different code types look their.