New in version 12.0: A new TCA type
folder has been introduced, which replaces the old
'type' => 'group' and
'internal_type' => 'folder'.
The TCA type
folder creates a field where folders can be attached to
the record. The values are stored as a combined identifier in a
comma-separated list (csv).
'columns' => [ 'aColumn' => [ 'config' => [ 'type' => 'folder', ], ], ],