How can I hide the shortcut toolbar in Drupal 8.6? I need the very top menu gone (the green part highlighted in screenshot).
The Toolbar module provides tabs (that you want to hide), and links related to those tabs. Since links are listed within the tab elements in HTML it isn't easy to just hide them with CSS.
But you can use the Toolbar Themes module.
Toolbar Themes configuration comes with the option not to use Toolbar tabs at all.
[ ] Show toolbar tabs
Unchecked this will remove tabs except for the Manage tab which is replaced by an icon.
Most people also install Admin Toolbar to get the drop-down menus, it significantly speeds up navigating and number of clicks.