Enable dropdown menu for menus in header block

Description of the need There are some genuine use cases where drop down menus are needed for a site's primary navigation but for a given theme, the best place for a menu is as part of the header block, either for the look or because the primary navigation block doesn't work well in that theme.

Proposed solution It would be good to enable the menu in the "Header block" to be a dropdown menu.

Alternatives that have been considered Some themes work quite well with having a primary navigation block in the header and the menu disabled in the header block.

Is there a Drupal or Backdrop contributed module that accomplishes this? Not aware