How do I load an entity? How can I load the entities shown in the following screenshot?
Use loadMultiple():

$storage = \Drupal::entityTypeManager()-&gt;getStorage('default_entity');
$config_entities = $storage-&gt;loadMultiple();
$list = [];
foreach ($config_entities as $id =&gt; $entity) {
  $list[$id] = $entity-&gt;label();
}