Redirect a WP page URL without a plugin or messing with domain DNS settings. Replace the [from slug] and [to slug] below the line starting with switch with the wp slugs for each URL (ie. [from slug] would be /tos , [to slug] would be /terms-of-service)

redirecturlsinwp.php

function redirect_page() {

     if (isset($_SERVER['HTTPS']) &&
        ($_SERVER['HTTPS'] == 'on' || $_SERVER['HTTPS'] == 1) ||
        isset($_SERVER['HTTP_X_FORWARDED_PROTO']) &&
        $_SERVER['HTTP_X_FORWARDED_PROTO'] == 'https') {
        $protocol = 'https://';
        }
        else {
        $protocol = 'http://';
    }

    $currenturl = $protocol . $_SERVER['HTTP_HOST'] . $_SERVER['REQUEST_URI'];
    $currenturl_relative = wp_make_link_relative($currenturl);

    switch ($currenturl_relative) {
    
        case '[from slug]':
            $urlto = home_url('[to slug]');
            break;
        
        default:
            return;
    
    }
    
    if ($currenturl != $urlto)
        exit( wp_redirect( $urlto ) );


}
add_action( 'template_redirect', 'redirect_page' );