how to create a drop down list inside nbcontextmenu – Nebular Angular11

Solution for how to create a drop down list inside nbcontextmenu – Nebular Angular11
is Given Below:

I am trying to put a menu like this

[Laptop view}1

and

mobile view

My menu :


  userMenu = [
    {title: 'Profile'},
    { title: 'Change Themes' },
    { title: 'Show Time ' },
    { title: 'Log out' },
  ];;

My html

    <nb-action class="user-action">
      <nb-user [nbContextMenu]="userMenu" [onlyPicture]="userPictureOnly" [name]="user?.userName">    
      </nb-user>
    </nb-action>

I want add drop down for change theme and show time
How can I do the . Any Idea?