Issue #3211578: D9 and Moderation Sidebar fixes

src/ScheduledTransitionsModerationSidebarHooks.php

@@ -113,7 +113,9 @@ class ScheduledTransitionsModerationSidebarHooks implements ContainerInjectionIn
     );
 
     if (count($rows) > 0) {
-      $build['scheduled_transitions'] = [
+      // Move to actions.secondary until issue is merged:
+      // https://www.drupal.org/project/moderation_sidebar/issues/3211572.
+      $build['actions']['secondary'] = [
         '#theme' => 'scheduled_transitions_sidebar_transitions',
         '#transitions' => $rows,
       ];