https://understanddrupal.com/articles/using-migration-groups-share-configuration-among-drupal-migrations

migration_group_with_shared_configuration.yml

uuid: e88e28cc-94e4-4039-ae37-c1e3217fc0c4
id: udm_config_group_csv_source
label: 'UD Config Group (CSV source)'
description: 'A container for migrations about individuals and their favorite books. Learn more at https://understanddrupal.com/migrations.'
source_type: 'CSV resource'
shared_configuration:
  dependencies:
    enforced:
      module:
        - ud_migrations_config_group_csv_source
  migration_tags:
    - UD Config Group (CSV Source)
    - UD Example
  source:
    plugin: csv
    # It is assumed that CSV files do not contain a headers row. This can be
    # overridden for migrations where that is not the case.
    header_offset: null

migration_group_without_shared_configuration.yml

uuid: e88e28cc-94e4-4039-ae37-c1e3217fc0c4
id: udm_config_group_csv_source
label: 'UD Config Group (CSV source)'
description: 'A container for migrations about individuals and their favorite books. Learn more at https://understanddrupal.com/migrations.'
source_type: 'CSV resource'
shared_configuration: null

migration_overriding_a_group_configuration.yml

uuid: 97179435-ca90-434b-abe0-57188a73a0bf
id: udm_config_group_csv_source_node
label: 'UD configuration host node migration for migration group example (CSV source)'
# Any configuration defined in the migration group can be overridden here
# by re-declaring the configuration and assigning a value.
# `dependencies` inherited from migration group.
# `migration_tags` inherited from migration group.
migration_group: udm_config_group_csv_source
source:
  # `plugin` inherited from migration group.
  path: modules/custom/ud_migrations/ud_migrations_csv_source/sources/udm_people.csv
  ids: [unique_id]
  # This overrides the `header_offset` defined in the group. The referenced CSV
  # file includes headers in the first row. Thus, a value of `0` is used.
  header_offset: 0
process: ...
destination: ...
migration_dependencies: ...

migration_specifing_a_group.yml

uuid: 97179435-ca90-434b-abe0-57188a73a0bf
id: udm_config_group_csv_source_node
label: 'UD configuration host node migration for migration group example (CSV source)'
migration_group: udm_config_group_csv_source
source: ...
process: ...
destination: ...
migration_dependencies: ...