Issue #3252215: Default domain values not being assigned while creating a new Entity

domain_entity.module

@@ -593,6 +593,21 @@ function domain_entity_field_widget_single_element_form_alter(&$element, FormSta
   if ($context['items']->getFieldDefinition()->getName() !== DomainEntityMapper::FIELD_NAME) {
     return;
   }
+  $form_object = $form_state->getFormObject();
+  if (!$form_object instanceof EntityFormInterface) {
+    return;
+  }
+  // Get the current Entity information.
+  $entity = $form_object->getEntity();
+
+  // Add Default value if we are creating a new Entity.
+  if ((is_object($entity)) && ($entity->isNew())) {
+    // Get active Domain ID.
+    $active_id = \Drupal::service('domain.negotiator')->getActiveId();
+
+    // Default value based on the current Active Domain.
+    $element['#default_value'] = [$active_id];
+  }
 
   $form_object = $form_state->getFormObject();
   if (!$form_object instanceof EntityFormInterface) {