lib/pages/collections_list_page.dart

@@ -20,6 +20,7 @@ class CollectionsListPage extends StatefulWidget {
 
 class _CollectionsListPageState extends State<CollectionsListPage> {
   bool addingNewBookmark = false;
+  final bookmarkCountMap = Storage.loadPerCollectionBookmarkCount();
 
   Widget bottomSheetBuilder(BuildContext context) {
     final titleTextFieldController = TextEditingController(
@@ -53,6 +54,11 @@ class _CollectionsListPageState extends State<CollectionsListPage> {
       title: Text(collection.name),
       onTap: () => navigateToCollection(collection.id),
       onLongPress: () => onEditCollection(collection),
+      leading: const Icon(Icons.list_rounded),
+      trailing: Text(
+        bookmarkCountMap[collection.id]?.toString() ?? '0',
+        style: Theme.of(context).textTheme.bodyMedium,
+      ),
     );
   }
 

lib/service/storage.dart

@@ -50,6 +50,14 @@ class Storage {
     return allBookmarks.where((b) => b.collectionId == collectionId).toList();
   }
 
+  static Map<int, int> loadPerCollectionBookmarkCount() {
+    return loadBookmarks().fold(<int, int>{}, (map, bookmark) {
+      map[bookmark.collectionId] ??= 0;
+      map[bookmark.collectionId] = map[bookmark.collectionId]! + 1;
+      return map;
+    });
+  }
+
   static Future<void> addBookmark(Bookmark bookmark) async {
     final bookmarks = loadBookmarks();
     bookmarks.add(bookmark);