Adds a new WooCommerce Settings Tab

wc-settings-tab.php

<?php
class WC_Settings_Tab_Demo {

    public static function init() {
        add_filter( 'woocommerce_settings_tabs_array', __CLASS__ . '::add_settings_tab', 50 );
    }

    public static function add_settings_tab( $settings_tabs ) {
        $settings_tabs['settings_tab_demo'] = __( 'Settings Demo Tab', 'woocommerce-settings-tab-demo' );
        return $settings_tabs;
    }
}
WC_Settings_Tab_Demo::init();