$app->getExecutorFactory()->registerTrigger(
    $app->getExecutorFactory()::TABLE_BUTTON,
    [Button::class, 'ui' => 'atk-test button', 'icon' => 'pencil'],
    $m->getUserAction('edit')
);

// Creating a button for executing model test user action.
$grid->addExecutorButton($grid->getExecutorFactory()->create($model->getUserAction('test'), $grid));

// Overriding basic ExecutorFactory in order to change Table and Modal button.
// and also changing default add action label.
class MyFactory extends ExecutorFactory {
    public const BUTTON_PRIMARY_COLOR = 'green';

    protected $triggerSeed = [
        self::TABLE_BUTTON => [
            'edit' => [Button::class, null, 'icon' => 'pencil'],
            'delete' => [Button::class, null, 'icon' => 'times red'],
        ],
        self::CARD_BUTTON => [
            'edit' => [Button::class, 'Edit', 'icon' => 'pencil', 'ui' => 'tiny button'],
            'delete' => [Button::class, 'Remove', 'icon' => 'times', 'ui' => 'tiny button'],
        ],
    ];

    protected $triggerCaption = [
        'add' => 'Add New Record',
    ];
}

// Overriding basic ExecutorFactory in order to change Card button.
class SpecialCardFactory extends ExecutorFactory {
    public const BUTTON_PRIMARY_COLOR = 'green';

    protected $actionIcon = [
        'callback' => 'sync',
        'preview' => 'eye',
        'edit_argument' => 'user edit',
        'edit_argument_prev' => 'pen square',
        'edit_iso' => 'pencil',
        'confirm' => 'check circle',
        'multi_step' => 'window maximize outline',
    ];

    public function __construct()
    {
        // registering card button default with our own method handler.
        $this->triggerSeed = array_merge(
            $this->triggerSeed,
            [self::CARD_BUTTON => ['default' => [$this, 'getCardButton']]]
        );
    }

    protected function getCardButton($action, $type)
    {
        return [Button::class, 'icon' => $this->actionIcon[$action->short_name]];
    }
}

$card = Card::addTo($app, ['useLabel' => true, 'executorFactory' => new SpecialCardFactory()]);
$card->setModel($country);

$country->addUserAction('mail', [
    'appliesTo' => \atk4\data\Model\UserAction::APPLIES_TO_SINGLE_RECORD,
    'preview' => function ($model) { return 'here is email preview for ' . $model->get('name'); },
    'callback' => function ($model) { return 'email sent to ' . $model->get('name'); },
    'description' => 'Email testing',
    'ui' => ['icon' => 'mail', 'button' => [null, 'icon' => 'green mail']],
 ]);

$country->addUserAction('mail', [
    'appliesTo' => \atk4\data\Model\UserAction::APPLIES_TO_SINGLE_RECORD,
    'preview' => function ($model) { return 'here is email preview for ' . $model->get('name'); },
    'callback' => function ($model) { return 'email sent to ' . $model->get('name'); },
    'description' => 'Email testing',
]);

// Register a trigger for mail action in Crud
$app->getExecutorFactory()->registerTrigger(
    $app->getExecutorFactory()::TABLE_BUTTON,
    [Button::class, null, 'icon' => 'green mail'],
    $country->getUserAction('mail')
);