Is it possible to use tokens in a menu link in Drupal8? I need to add an option to "User account Menu" that shows the current user name. It is possible to do this using tokens or some other method?

Thanks!
No, you cannot use tokens in menus out of the box.

Here are some options:


Use Views to create the link.  This won't give you a menu, but you can make a block in Views and use that as a menu.  You may have to hard-code the rest of your "menu" in the views block, which isn't ideal but if you can't code that may be your best option for now. 
Code the menu link.  See the routes documentation.
Watch the progress of the Menu Token module.  This module does what you want but it doesn't have a stable release for Drupal 8 yet.  I haven't used the D8 version so I don't know how well it works at the moment.