muser-8.x-1.x-dev/modules/custom/muser_system/muser_system.links.task.yml

muser_system.config:
  title: 'Settings'
  route_name: muser_system.config
  base_route: muser_system.config
  weight: 0

muser_system.email_settings:
  route_name: muser_system.email_settings
  base_route: muser_system.config
  title: 'Email settings'
  weight: 10