Difficulty adding a parent menu link I'm creating a custom module in Drupal 8.4.4. I put several menu links under the Development menu.

scrape.scrape_form:
  title: 'Scrape'
  parent: system.admin_config_development
  route_name: scrape.scrape_form
  description: 'Scrape content from ccad.edu'
  weight: 10

scrape.scrape_images_form:
  title: 'Images Scrape'
  parent: system.admin_config_development
  route_name: scrape.scrape_images_form
  description: 'Scrape images from ccad.edu'
  weight: 20

...


This is working fine, but now that whole menu is getting a bit too long. 

I wanted to wrap up all of my links under one 'header' link under the Development menu.  I added this at the top of mymodule.links.menu.yml:

scrape.migration:
  title: 'Migration'
  description: 'Migration functions'
  parent: system.admin_config_development
  route:&lt;nolink&gt;
  menu_name: scrape.migration
  route_name: scrape.migration


But when I try to rebuild the cache, I get this error: 

The website encountered an unexpected error. Please try again later. Symfony\Component\Routing\Exception\RouteNotFoundException: Route &amp;quot;scrape.migration&amp;quot; does not exist. in Drupal\Core\Routing\RouteProvider-&gt;getRouteByName()


How can I make a new, non-navigable parent link under Development, to put my custom links under?

Edit 4k4's comment is correct, but my parent link is very small and greyed out.

scrape.migration:
  title: 'Migration'
  description: 'Migration functions'
  parent: system.admin_config_development
  menu_name: scrape.migration
  route_name: &lt;nolink&gt;




How can I get a full-height, dark-font header link?
Instead of using route_name: &lt;nolink&gt;, I suggest providing a route for the link and e.g. pointing that route to Drupal's default overview page contoller. This should fix your issue and assures the users can click the menu link and get an overview of the available functions (e.g. when re-using your module in a Drupal that has no Admin Toolbar installed):

mymodule.links.menu.yml

scrape.migration:
  title: 'Migration'
  description: 'Migration functions'
  parent: system.admin_config_development
  route_name: scrape.migration


mymodule.routing.yml

scrape.migration:
  path: '/admin/config/development/scrape'
  defaults:
    _controller: '\Drupal\system\Controller\SystemController::overview'
    link_id: 'scrape.migration'
    _title: 'Migration'
  requirements:
    _permission: 'access administration pages'


You might have to adapt the path/permissions accordingly.