Change WooCommerce Order pay page title
Updated
You can use the following to change "Pay for order" page title:
add_filter( 'the_title', 'change_pay_for_order_title' );function change_pay_for_order_title( $title ) { if ( is_wc_endpoint_url( 'order-pay' ) ) { return __('Checkout', 'woocommerce'); } return $title;}Or also the following code based on 'order-pay' endpoint (but changes the breadcrumb):
add_filter( 'woocommerce_endpoint_order-pay_title', 'change_checkout_order_pay_title' );function change_checkout_order_pay_title( $title ) { return __( "Checkout", "woocommerce" );}Code goes in functions.php file of the active child theme (or active theme). Tested and works.
Related: Set My Account custom items endpoints titles in WooCommerce