bat-8.x-1.x-dev/modules/bat_event_series/bat_event_series.links.menu.yml

entity.bat_event_series.collection:
  title: 'Event Series'
  route_name: entity.bat_event_series.collection
  description: 'List of event Series'
  parent: bat.admin.events
  weight: 11

entity.bat_event_series_type.collection:
  title: 'Event series Types'
  route_name: entity.bat_event_series_type.collection
  description: 'List of event series Types'
  parent: bat.admin.events
  weight: 12