add username in menu dynamically OR dynamic text add in menu

Function.php

class Walker_Sugarfun_Menu extends Walker {
    function start_el( &$output, $item, $depth = 0, $args = array(), $id = 0 ) {
      $pagename = get_query_var('pagename');


      $user = wp_get_current_user();
      if(bp_current_component() == 'members')
        $pageName = 'FIND YOUR FUN';
      else if(bp_current_component() == 'messages')
        $pageName = 'MESSAGES';
      else if(bp_current_component() == 'following')
        $pageName = 'FAVOURITES';
      else if(tribe_is_month()==1 && $item->title == 'SUGAR EVENTS')
        $pageName = 'SUGAR EVENTS';
      else if( $item->title == 'MY ACCOUNT')
        $pageName = 'MY ACCOUNT';

$className = '';
      if($pageName == $item->title)
        $className = 'active-nav-page';
     
      $output .= sprintf( "\n<li class='$className'><a href='%s'%s>%s ".$messageText."</a></li>\n",
            str_replace("--username--", $user->user_login, $item->url),
            ( $item->object_id === get_the_ID() ) ? ' class="current"' : '',
            $item->title
        );


}


OR


add_filter( 'nav_menu_link_attributes', 'menu_override', 10, 3 );
function menu_override( $atts, $item, $args ) {
    $user = wp_get_current_user();
    $newlink = str_replace("--username--", $user->user_login, $atts['href']);
    $atts[href] = $newlink;
    return $atts;
}