Changing Sub-menu's name

Hi, thank you for this plugin.

I haven’t been able to use it since i’m still in the process of developing a website for a client. I have a question, is there a way to rename the sub-menu item that’s under the main “Dashboard” menu item ?

I have been using :
$submenu['index.php'][20][0] = 'Tracker';
and tried with a lot of different numbers…

Also i tried to remove the menu item to create another with a different title… No luck again :
remove_submenu_page('index.php','user-online');

Can you help me,
Thank you very much indeed,

Ivan

https://ww.wp.xz.cn/plugins/wp-useronline/