Export Types
Extend Freeform Exporting capabilities by adding your own export types:
Registering Custom Export Types
Use this event to attach your own export types.
First, create your own export type, which extends the Export Interface:
<?php
namespace My\Exporter;
use Solspace\Freeform\Library\Export\ExportInterface;
use Solspace\Freeform\Library\Composer\Components\Form;
class CustomExport implements ExportInterface
{
    private $submissionData;
    public function __construct(Form $form, array $submissionData)
    {
        $this->submissionData = $submissionData;
    }
    public static function getLabel(): string
    {
        return 'Custom Export';
    }
    public function getMimeType(): string
    {
        return 'text/html';
    }
    public function getFileExtension(): string
    {
        return 'html';
    }
    public function export()
    {
        return '<html><body><pre>'.json_encode($this->submissionData).'</pre></body></html>';
    }
}
Then register your exporter:
use Solspace\Freeform\Services\ExportProfilesService;
use Solspace\Freeform\Events\ExportProfiles\RegisterExporterEvent;
use My\Exporter\CustomExport;
Event::on(
  ExportProfilesService::class,
  ExportProfilesService::EVENT_REGISTER_EXPORTER,
  function (RegisterExporterEvent $event) {
    $event->addExporter(
      'custom_export',
      CustomExport::class
    );
  }
);
You should now see your custom export type available in the export profiles view and in the quick export pop-up.