charts-8.x-4.x-dev/tests/modules/charts_test/config/schema/charts_test.schema.yml

charts.settings.library_plugin.charts_test_library:
  type: mapping
  mapping:
    foo:
      label: Foo
      type: string

charts.library_plugin.charts_test_library.options.column:
  label: 'Charts Test Library library Column type options'
  type: mapping