Submit function set by tmgmt_content_form_tmgmt_settings_form_alter().
function tmgmt_content_settings_submit(array &$form, FormStateInterface $form_state) {
$embedded_fields = array();
foreach ($form_state
->getValue('embedded_fields', []) as $key => $fields) {
foreach (array_filter($fields) as $id => $label) {
$embedded_fields[$key][$id] = TRUE;
}
}
\Drupal::configFactory()
->getEditable('tmgmt_content.settings')
->set('embedded_fields', $embedded_fields)
->set('default_moderation_states', $form_state
->getValue('default_moderation_states', []))
->save();
}