better forms

app/helpers/admin/application_helper.rb

@@ -81,6 +81,21 @@ module Admin::ApplicationHelper
     collection
   end
 
+  def collection_tree_for_checkboxes(list, except = nil)
+    collection = collection_tree(list, except)
+    collection.map { |object|
+      [
+        sanitize(object[:label]),
+        object[:id],
+        {
+          data: {
+            parent: object[:parent_id]
+          }
+        }
+      ]
+    }
+  end
+
   private
 
   def polymorphic_url_param(object_or_class, **options)

app/views/admin/communication/website/posts/_form.html.erb

@@ -11,6 +11,17 @@
           <%= f.input :text, as: :rich_text_area %>
         </div>
       </div>
+      <div class="card flex-fill w-100">
+        <div class="card-header">
+          <h5 class="card-title mb-0"><%= t('activerecord.attributes.communication/website/post.categories') %></h5>
+        </div>
+        <div class="card-body">
+          <%= f.association :categories,
+                            label_text: false,
+                            as: :check_boxes,
+                            collection: collection_tree_for_checkboxes(@website.categories) if @website.categories.any? %>
+        </div>
+      </div>
     </div>
     <div class="col-md-4">
       <div class="card flex-fill w-100">
@@ -28,13 +39,6 @@
           <%= f.input :published_at, html5: true %>
           <%= f.input :pinned %>
           <%= f.association :author, collection: current_university.people.authors.ordered %>
-          <%= f.association :categories,
-                            as: :check_boxes,
-                            collection: collection_tree(@website.categories).map { |category| [
-                              sanitize(category[:label]),
-                              category[:id],
-                              { data: { parent: category[:parent_id] } }
-                            ] } if @website.categories.any? %>
         </div>
       </div>
       <div class="card flex-fill w-100">