farm-2.x-dev/modules/core/notification/farm_notification.links.task.yml

farm_notification.settings:
  base_route: farm_settings.settings_page
  route_name: farm_notification.settings
  title: 'Notifications'
  weight: 5

# Provide a default sub tab.
farm_notification.settings_sub:
  title: 'Notifications'
  route_name: farm_notification.settings
  parent_id: farm_notification.settings
  weight: -5