bookmark dropped in a menu between the last bookmark and the 'open in tab' menuseparator are inserted after the menuseparator. Quick fix by hiding the menuseparator before the drop and by showing it again after.

browser/base/content/browser.js

@@ -2009,25 +2009,45 @@ var personalToolbarDNDObserver = {
 
   onDrop: function (aEvent, aXferData, aDragSession)
   {
-    this.onDragRemoveFeedBack(aEvent.originalTarget);
-    var bt          = document.getElementById("bookmarks-toolbar");
-    var selection   = BookmarksUtils.getSelectionFromXferData(aDragSession);
+    var target = aEvent.originalTarget;
+    this.onDragRemoveFeedBack(target);
+
+    var bt        = document.getElementById("bookmarks-toolbar");
+    var selection = BookmarksUtils.getSelectionFromXferData(aDragSession);
 
     // if the personal toolbar does not exist, recreate it
-    if (aEvent.originalTarget == "bookmarks-toolbar") {
+    if (target == "bookmarks-toolbar") {
       //BookmarksUtils.recreatePersonalToolbarFolder(transactionSet);
       //target = { parent: "NC:PersonalToolbarFolder", index: 1 };
     } else {
       var orientation = bt.getBTOrientation(aEvent);
-      var target      = bt.getBTTarget(aEvent.originalTarget, orientation);
+      var selTarget   = bt.getBTTarget(aEvent.originalTarget, orientation);
     }
 
     const kDSIID      = Components.interfaces.nsIDragService;
     const kCopyAction = kDSIID.DRAGDROP_ACTION_COPY + kDSIID.DRAGDROP_ACTION_LINK;
+
+    // hide the 'open in tab' menuseparator because bookmarks
+    // can be inserted after it if they are dropped after the last bookmark
+    // a more comprehensive fix would be in the menupopup template builder
+    var menuTarget = target.parentNode;
+    if (menuTarget.hasChildNodes() &&
+        menuTarget.lastChild.id == "openintabs-menuitem") {
+      menuTarget.removeChild(menuTarget.lastChild.previousSibling);
+    }
+
     if (aDragSession.dragAction & kCopyAction)
-      BookmarksUtils.insertSelection("drag", selection, target, true);
+      BookmarksUtils.insertSelection("drag", selection, selTarget, true);
     else
-      BookmarksUtils.moveSelection("drag", selection, target);
+      BookmarksUtils.moveSelection("drag", selection, selTarget);
+
+    // show again the menuseparator
+    if (menuTarget.hasChildNodes() &&
+        menuTarget.lastChild.id == "openintabs-menuitem") {
+      var element = document.createElementNS(XUL_NS, "menuseparator");
+      menuTarget.insertBefore(element, menuTarget.lastChild);
+    }
+
   },
 
   canDrop: function (aEvent, aDragSession)
@@ -2244,16 +2264,17 @@ var personalToolbarDNDObserver = {
 
   onDragRemoveFeedBack: function (aTarget)
   { 
+    var newTarget;
     if (aTarget.localName == "hbox") { 
       // hit when dropping in the bt or between the last visible bookmark 
       // and the chevron
       var bt = document.getElementById("bookmarks-toolbar");
-      var newTarget = bt.getLastVisibleBookmark();
+      newTarget = bt.getLastVisibleBookmark();
       if (newTarget)
         newTarget.removeAttribute("dragover-right");
     } else if (aTarget.localName == "stack") {
       var bt = document.getElementById("bookmarks-toolbar");
-      var newTarget = bt.getLastVisibleBookmark();
+      newTarget = bt.getLastVisibleBookmark();
       newTarget.removeAttribute("dragover-right");
     } else {
       aTarget.removeAttribute("dragover-left");