bbb-8.x-1.x-dev/modules/bbb_node/bbb_node.links.action.yml

bbb_node.type_add:
  route_name: entity.bbb_node_type.add
  title: 'Add BigBlueButton content type'
  appears_on:
    - entity.bbb_node_type.collection

#bbb.meeting.end:
#  route_name: entity.bbb_node_type.add
#  title: 'Add BigBlueButton content type'
#  appears_on:
#    - entity.bbb_node_type.collection