ct_wizard_content_entity_example.routing.yml

entity.my_entity.wizard:
  path: '/my_entity/wizard/{my_entity_type}'
  defaults:
    _entity_wizard: 'my_entity.add_simple'
    _title: 'Simple My Entity Add Wizard'
    tempstore_id: 'ct_wizard_content_entity_example.my_entity'
  requirements:
    _permission: 'administer site configuration'
  options:
    parameters:
      my_entity_type:
        type: entity:my_entity_type
    _admin_route: TRUE

entity.my_entity.add_simple_step_form:
  path: '/my_entity/wizard/{my_entity_type}/{step}'
  defaults:
    _entity_wizard: 'my_entity.add_simple'
    _title: 'Simple My Entity Add Wizard Step'
    tempstore_id: 'ct_wizard_content_entity_example.my_entity'
  requirements:
    _permission: 'administer site configuration'
  options:
    parameters:
      my_entity_type:
        type: entity:my_entity_type
    _admin_route: TRUE