Editing CSV export fields for a specific group

_config.yml

Group:
  extensions:
    - GroupExtension

GroupExtension.php

<?php

class GroupExtension extends Extension {
  
  public function updateCMSFields($fields) {
    $gridField = $fields->dataFieldByName('Members');
    $exportButton = $gridField->getConfig()->getComponentByType('GridFieldExportButton');
    $exportButton->setExportColumns(array(
      'FirstName' => 'First name',
      'Surname' => 'Last name',
      'Email' => 'Email',
      'LastVisited' => 'Last visited'
    ));
  }
  
}