Functions to Add Settings to a WooCommerce Settings Tab

woocommerce-add-settings.php

<?php
add_action( 'woocommerce_settings_tabs_settings_tab_demo', 'settings_tab' );

function settings_tab() {
    woocommerce_admin_fields( get_settings() );
}

function get_settings() {
    $settings = array(
        'section_title' => array(
            'name'     => __( 'Section Title', 'woocommerce-settings-tab-demo' ),
            'type'     => 'title',
            'desc'     => '',
            'id'       => 'wc_settings_tab_demo_section_title'
        ),
        'title' => array(
            'name' => __( 'Title', 'woocommerce-settings-tab-demo' ),
            'type' => 'text',
            'desc' => __( 'This is some helper text', 'woocommerce-settings-tab-demo' ),
            'id'   => 'wc_settings_tab_demo_title'
        ),
        'description' => array(
            'name' => __( 'Description', 'woocommerce-settings-tab-demo' ),
            'type' => 'textarea',
            'desc' => __( 'This is a paragraph describing the setting. Lorem ipsum yadda yadda yadda. Lorem ipsum yadda yadda yadda. Lorem ipsum yadda yadda yadda. Lorem ipsum yadda yadda yadda.', 'woocommerce-settings-tab-demo' ),
            'id'   => 'wc_settings_tab_demo_description'
        ),
        'section_end' => array(
             'type' => 'sectionend',
             'id' => 'wc_settings_tab_demo_section_end'
        )
    );
    return apply_filters( 'wc_settings_tab_demo_settings', $settings );
}