I have tried this code but it is not working.
$form['field_test'] = [ '#title' => t('test'), '#type' => 'radios', '#options' => [t('A'), t('B'), t('C')], ]; $form['#group_children']['field_test'] = 'group_1';
I also tried with
$form['#fieldgroups']['group_1']->children = 'field_test';
But nothing is working. It works in Drupal 7. Is it changed in Drupal 8?
I have written this code in
hook_form_alter and I'm altering a node form.