this code permit to change the message "The product is already in quote request list!"
<?php
if ( function_exists( 'YITH_Request_Quote' ) ) {
add_filter( 'ywraq_product_in_list', 'ywraq_custom_product_in_list_message' );
function ywraq_custom_product_in_list_message( $message ) {
$message = sprintf( __( 'The product is already in quote request list! Please visit <a href="%s">here</a> to add more quantity.', 'yith-woocommerce-request-a-quote' ), YITH_Request_Quote()->get_raq_page_url() );
return $message;
}
}