Description of the bug

The admin_bar settings have a default where the option "Keep bar at top of page" is checked. This is a problem when navigating long menus like admin/config where the bottom items cannot be reached.

Steps To Reproduce

To reproduce the behavior:

1. Go to 'admin/config/administration/admin-bar' and confirm the setting "Keep bar at top of page" is checked.
2. However over the Adminbar Config item.
3. Scroll down to view all menu items and also pause to look at child menu items to see if the bottom items are visible.
4. It may be necessary to reduce the size of the browser window to see this problem.

Expected behavior

Ideally, it should be possible to scroll down and view all menu items.

The work around is to change the admin bar settings and uncheck "Keep bar at top of page", that raises the question: should the default be to have this setting unchecked?

Additional information

The problem was noted 16 years ago with Drupal 7, https://www.drupal.org/node/687750

Efforts where made and patches suggested for Drupal 7, https://www.drupal.org/project/admin_menu/issues/687750#comment-9677137 and https://www.drupal.org/project/admin_menu/issues/687750#comment-12038037 that worked partially but not completely. Further work is required to solve this issue. The patches by @a.hover @msmithcti and @robertgarrigos may provide a starting point.