Can not put placeholder in state field

The PHP line looks alright, but I have no other information as to where and in what context it is used.

First it needs to be included within the callback function of the “woocommerce_checkout_fields” filter. As follows:

add_filter( 'woocommerce_checkout_fields' , 'custom_override_checkout_fields' );

function custom_override_checkout_fields( $fields ) {
     $fields['billing']['billing_state']['placeholder'] = 'District';
     return $fields;
}

Secondly, the PHP snippet needs to go in the child theme’s functions.php file or it needs to be added to the website with the help of a plugin similar to Code Snippets.

Note that the input placeholder has nothing to do with the multi-step checkout plugin. If you successfully change the placeholder with the multi-step checkout plugin deactivated, then it should work with the plugin activated.