In the same page, I have two form : one for contact with elementor widget form and the second with elementor widget Acy for newsletter.

With

if ($widget->get_id()) {
            $fields = ['' => ''];
            foreach ($widget->get_data('settings')['form_fields'] as $field) {
                $fields[$field['custom_id']] = $field['field_label'];
            }

            $widget->start_controls_section('section_acymailing', [
                'label' => 'AcyMailing',
                'condition' => [
                    'submit_actions' => $this->get_name(),
                ],
            ]);

Warning: Undefined array key "field_label" in /home/wp-content/plugins/acymailing/wpinit/elementorForm.php on line 25

it's ok with

if ($widget->get_id() === 'acym_module_formAcym70581') {
    $fields = ['' => ''];
    foreach ($widget->get_data('settings')['form_fields'] as $field) {
        $fields[$field['custom_id']] = $field['field_label'];
    }

    $widget->start_controls_section('section_acymailing', [
        'label' => 'AcyMailing',
        'condition' => [
            'submit_actions' => $this->get_name(),
        ],
    ]);
}

But I think it's not very clean