Issue #3412897 Support displaying transition buttons as a dropbutton

src/Form/StateTransitionForm.php

@@ -113,15 +113,30 @@ class StateTransitionForm extends FormBase implements StateTransitionFormInterfa
       return;
     }
 
-    $form['actions'] = [
-      '#type' => 'container',
-    ];
+    $display_dropbuttons = $form_state->get('display_dropbuttons');
+    if ($display_dropbuttons) {
+      $form['actions'] = [
+        '#type' => 'actions',
+        '#suffix' => '<div class="clearfix"></div>',
+      ];
+    }
+    else {
+      $form['actions'] = [
+        '#type' => 'container',
+      ];
+    }
+
     // Determine whether we should output links to the confirmation form,
     // or submit buttons.
     $require_confirmation = $form_state->get('require_confirmation');
     foreach ($state_item->getTransitions() as $transition_id => $transition) {
+      $form['actions'][$transition_id] = [];
+      if ($display_dropbuttons) {
+        $form['actions'][$transition_id]['#dropbutton'] = 'state';
+      }
+
       if (!$require_confirmation) {
-        $form['actions'][$transition_id] = [
+        $form['actions'][$transition_id] += [
           '#type' => 'submit',
           '#value' => $transition->getLabel(),
           '#submit' => ['::submitForm'],
@@ -136,7 +151,7 @@ class StateTransitionForm extends FormBase implements StateTransitionFormInterfa
         'transition_id' => $transition_id,
       ];
 
-      $form['actions'][$transition_id] = [
+      $form['actions'][$transition_id] += [
         '#type' => 'link',
         '#title' => $transition->getLabel(),
         '#url' => Url::fromRoute("entity.{$this->entity->getEntityTypeId()}.state_transition_form", $route_parameters, [