Migrating into custom node type with multi value field I'm doing a migration into D8, and I'm migrating into a custom video player field with multiple values. Here's the schema for the field as defined in its plugin:

  public static function schema(FieldStorageDefinitionInterface $field_definition) {
    return array(
      'columns' =&gt; array(
        'vid' =&gt; array(
          'type' =&gt; 'int',
          'size' =&gt; 'normal',
          'not null' =&gt; TRUE,
          'default' =&gt; 0,
        ),
        'video' =&gt; array(
          'type' =&gt; 'varchar',
          'length' =&gt; 256,
          'not null' =&gt; FALSE,
        ),
        'video_hd' =&gt; array(
          'type' =&gt; 'varchar',
          'length' =&gt; 256,
          'not null' =&gt; FALSE,
        ),
        'video_sm' =&gt; array(
          'type' =&gt; 'varchar',
          'length' =&gt; 256,
          'not null' =&gt; FALSE,
        ),
        'thumbnail' =&gt; array(
          'type' =&gt; 'varchar',
          'length' =&gt; 256,
          'not null' =&gt; FALSE,
        ),
        'poster' =&gt; array(
          'type' =&gt; 'varchar',
          'length' =&gt; 256,
          'not null' =&gt; FALSE,
        ),
        'show_ads' =&gt; array(
          'type' =&gt; 'int',
          'size' =&gt; 'tiny',
          'not null' =&gt; TRUE,
          'default' =&gt; '1',
        ),
        'raw_file' =&gt; array(
          'type' =&gt; 'varchar',
          'length' =&gt; 256,
          'not null' =&gt; FALSE,
        ),
      ),
    );
  }


I have a custom source plugin that gathers all of the information needed for these columns into appropriately named items. My question is, how do I get those pieces of data into the destination field. Can I do it in the .yml file configuration, as can be done with the body field?

  'body/format':
    plugin: migration
    migration: d6_filter_format
    source: format
  'body/value': node_body
  'body/summary': teaser


Or do I need to have a custom destination plugin that takes these pieces of data and puts them into the correct places in the node? I'm seeing a lot of blogs and documentation on source and process plugins, but not much on destination plugins, so I'm not sure.

Thanks.
Nothing to do with destination plugins, what you need to do would be in the process pipeline. You could write a custom process plugin like, say, d6_cck_link. Or, you can use the iterator process plugin - see, for example, how d6_upload.yml in core populates the target_id/display/description columns of the 'upload' field.