What is the parent name for the admin menu? what is the parent name for the admin menu ?  if I put system.admin_structure in the mymodule.links.menu.yml file as below, it places the new menu item under the structure tab on the menu.  How do I get it on the first level of the menu.?
mymodule.demo:

title: Demo Link
  description: 'This is a demo link'
  parent: system.admin_structure
  url: 'internal:/taxonomy/term/3'
  //route_name: entity.taxonomy_vocabulary.overview_form
  menu_name: admin
  weight: -79
parent:system.admin is the answer , obvious wasn't it.