In Bookmark manager 'Add page' and 'Add Folder' always add new page or folder at the end.

chrome/browser/resources/bookmark_manager/js/main.js

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 (function() {
 /** @const */ var BookmarkList = bmm.BookmarkList;
 /** @const */ var BookmarkTree = bmm.BookmarkTree;
 /** @const */ var Command = cr.ui.Command;
 /** @const */ var LinkKind = cr.LinkKind;
 /** @const */ var ListItem = cr.ui.ListItem;
@@ skipping 1011 matching lines @@
 
 /**
  * Callback for the new folder command. This creates a new folder and starts
  * a rename of it.
  * @param {EventTarget=} opt_target The target to create a new folder in.
  */
 function newFolder(opt_target) {
   performGlobalUndo = null;  // This can't be undone, so disable global undo.
 
   var parentId = computeParentFolderForNewItem();
-
+  var selectedItem = bmm.list.selectedItem;
+  var newIndex;
   // Callback is called after tree and list data model updated.
   function createFolder(callback) {
+    if (selectedItem && document.activeElement != bmm.tree &&
+        !bmm.isFolder(selectedItem)) {
+      newIndex = bmm.list.dataModel.indexOf(selectedItem) + 1;
+    }
     chrome.bookmarks.create({
       title: loadTimeData.getString('new_folder_name'),
-      parentId: parentId
+      parentId: parentId,
+      index: newIndex
     }, callback);
   }
 
   if ((opt_target || document.activeElement) == bmm.tree) {
     createFolder(function(newNode) {
       navigateTo(newNode.id, function() {
         bmm.treeLookup[newNode.id].editing = true;
       });
     });
     return;
   }
 
   function editNewFolderInList() {
-    createFolder(function() {
-      var index = bmm.list.dataModel.length - 1;
+    createFolder(function(newNode) {
+      var index = newNode.index;
       var sm = bmm.list.selectionModel;
       sm.anchorIndex = sm.leadIndex = sm.selectedIndex = index;
       scrollIntoViewAndMakeEditable(index);
     });
   }
 
   navigateTo(parentId, editNewFolderInList);
 }
 
 /**
@@ skipping 10 matching lines @@
       item.editing = true;
   }, 0);
 }
 
 /**
  * Adds a page to the current folder. This is called by the
  * add-new-bookmark-command handler.
  */
 function addPage() {
   var parentId = computeParentFolderForNewItem();
+  var selectedItem = bmm.list.selectedItem;
+  var newIndex;
+  function editNewBookmark() {
+    if (selectedItem && document.activeElement != bmm.tree &&
+        !bmm.isFolder(selectedItem)) {
+      newIndex = bmm.list.dataModel.indexOf(selectedItem) + 1;
+    }
 
-  function editNewBookmark() {
     var fakeNode = {
       title: '',
       url: '',
       parentId: parentId,
+      index: newIndex,
       id: 'new'
     };
     var dataModel = bmm.list.dataModel;
-    var length = dataModel.length;
-    dataModel.splice(length, 0, fakeNode);
+    var index = dataModel.length;
+    if (newIndex != undefined)
+      index = newIndex;
+    dataModel.splice(index, 0, fakeNode);
     var sm = bmm.list.selectionModel;
-    sm.anchorIndex = sm.leadIndex = sm.selectedIndex = length;
-    scrollIntoViewAndMakeEditable(length);
+    sm.anchorIndex = sm.leadIndex = sm.selectedIndex = index;
+    scrollIntoViewAndMakeEditable(index);
   };
 
   navigateTo(parentId, editNewBookmark);
 }
 
 /**
  * This function is used to select items after a user action such as paste, drop
  * add page etc.
  * @param {BookmarkList|BookmarkTree} target The target of the user action.
  * @param {string=} opt_selectedTreeId If provided, then select that tree id.
@@ skipping 384 matching lines @@
 
   cr.ui.FocusOutlineManager.forDocument(document);
   initializeSplitter();
   bmm.addBookmarkModelListeners();
   dnd.init(selectItemsAfterUserAction);
   bmm.tree.reload();
 }
 
 initializeBookmarkManager();
 })();