diff --git a/Pdf4QtDocPageOrganizer/mainwindow.cpp b/Pdf4QtDocPageOrganizer/mainwindow.cpp
index 3db4880..2763033 100644
--- a/Pdf4QtDocPageOrganizer/mainwindow.cpp
+++ b/Pdf4QtDocPageOrganizer/mainwindow.cpp
@@ -253,6 +253,7 @@ bool MainWindow::canPerformOperation(Operation operation) const
 {
     QModelIndexList selection = ui->documentItemsView->selectionModel()->selection().indexes();
     const bool isSelected = !selection.isEmpty();
+    const bool isMultiSelected = selection.size() > 1;
     const bool isModelEmpty = m_model->rowCount(QModelIndex()) == 0;
 
     switch (operation)
@@ -263,7 +264,7 @@ bool MainWindow::canPerformOperation(Operation operation) const
             return isSelected;
 
         case Operation::RestoreRemovedItems:
-            return !m_trashBin.empty();
+            return !m_model->isTrashBinEmpty();
 
         case Operation::Cut:
         case Operation::Copy:
@@ -277,7 +278,7 @@ bool MainWindow::canPerformOperation(Operation operation) const
             return isSelected;
 
         case Operation::Group:
-            return isSelected;
+            return isMultiSelected;
         case Operation::Ungroup:
             return m_model->isGrouped(selection);
 
@@ -323,10 +324,15 @@ void MainWindow::performOperation(Operation operation)
         case Operation::Paste:
         case Operation::RotateLeft:
         case Operation::RotateRight:
+            Q_ASSERT(false);
             break;
 
         case Operation::Group:
+            m_model->group(ui->documentItemsView->selectionModel()->selection().indexes());
+            break;
+
         case Operation::Ungroup:
+            m_model->ungroup(ui->documentItemsView->selectionModel()->selection().indexes());
             break;
 
         case Operation::SelectNone:
diff --git a/Pdf4QtDocPageOrganizer/mainwindow.h b/Pdf4QtDocPageOrganizer/mainwindow.h
index 1f179f0..6cfad83 100644
--- a/Pdf4QtDocPageOrganizer/mainwindow.h
+++ b/Pdf4QtDocPageOrganizer/mainwindow.h
@@ -102,7 +102,6 @@ private:
     PageItemDelegate* m_delegate;
     Settings m_settings;
     QSignalMapper m_mapper;
-    std::vector<PageGroupItem> m_trashBin;
 };
 
 }   // namespace pdfdocpage
diff --git a/Pdf4QtDocPageOrganizer/pageitemmodel.cpp b/Pdf4QtDocPageOrganizer/pageitemmodel.cpp
index ce448ff..00b982a 100644
--- a/Pdf4QtDocPageOrganizer/pageitemmodel.cpp
+++ b/Pdf4QtDocPageOrganizer/pageitemmodel.cpp
@@ -125,6 +125,19 @@ const PageGroupItem* PageItemModel::getItem(const QModelIndex& index) const
     return nullptr;
 }
 
+PageGroupItem* PageItemModel::getItem(const QModelIndex& index)
+{
+    if (index.isValid())
+    {
+        if (index.row() < m_pageGroupItems.size())
+        {
+            return &m_pageGroupItems.at(index.row());
+        }
+    }
+
+    return nullptr;
+}
+
 bool PageItemModel::isGrouped(const QModelIndexList& indices) const
 {
     for (const QModelIndex& index : indices)
@@ -161,6 +174,88 @@ QItemSelection PageItemModel::getSelectionLandscape() const
     return getSelectionImpl([](const PageGroupItem::GroupItem& groupItem) { return groupItem.rotatedPageDimensionsMM.width() >= groupItem.rotatedPageDimensionsMM.height(); });
 }
 
+void PageItemModel::group(const QModelIndexList& list)
+{
+    if (list.isEmpty())
+    {
+        return;
+    }
+
+    std::vector<size_t> groupedIndices;
+    groupedIndices.reserve(list.size());
+    std::transform(list.cbegin(), list.cend(), std::back_inserter(groupedIndices), [](const auto& index) { return index.row(); });
+    std::sort(groupedIndices.begin(), groupedIndices.end());
+
+    std::vector<PageGroupItem> newPageGroupItems;
+    std::vector<PageGroupItem::GroupItem> newGroups;
+    newPageGroupItems.reserve(m_pageGroupItems.size());
+    for (size_t i = 0; i < m_pageGroupItems.size(); ++i)
+    {
+        const PageGroupItem& item = m_pageGroupItems[i];
+        if (std::binary_search(groupedIndices.cbegin(), groupedIndices.cend(), i))
+        {
+            newGroups.insert(newGroups.end(), item.groups.begin(), item.groups.end());
+        }
+        else
+        {
+            newPageGroupItems.push_back(item);
+        }
+    }
+
+    PageGroupItem newItem;
+    newItem.groups = qMove(newGroups);
+    updateItemCaptionAndTags(newItem);
+    newPageGroupItems.insert(std::next(newPageGroupItems.begin(), groupedIndices.front()), qMove(newItem));
+
+    if (newPageGroupItems != m_pageGroupItems)
+    {
+        beginResetModel();
+        m_pageGroupItems = std::move(newPageGroupItems);
+        endResetModel();
+    }
+}
+
+void PageItemModel::ungroup(const QModelIndexList& list)
+{
+    if (list.isEmpty())
+    {
+        return;
+    }
+
+    std::vector<size_t> ungroupedIndices;
+    ungroupedIndices.reserve(list.size());
+    std::transform(list.cbegin(), list.cend(), std::back_inserter(ungroupedIndices), [](const auto& index) { return index.row(); });
+    std::sort(ungroupedIndices.begin(), ungroupedIndices.end());
+
+    std::vector<PageGroupItem> newPageGroupItems;
+    newPageGroupItems.reserve(m_pageGroupItems.size());
+    for (size_t i = 0; i < m_pageGroupItems.size(); ++i)
+    {
+        const PageGroupItem& item = m_pageGroupItems[i];
+        if (item.isGrouped() && std::binary_search(ungroupedIndices.cbegin(), ungroupedIndices.cend(), i))
+        {
+            for (const PageGroupItem::GroupItem& groupItem : item.groups)
+            {
+                PageGroupItem newItem;
+                newItem.groups = { groupItem };
+                updateItemCaptionAndTags(newItem);
+                newPageGroupItems.push_back(qMove(newItem));
+            }
+        }
+        else
+        {
+            newPageGroupItems.push_back(item);
+        }
+    }
+
+    if (newPageGroupItems != m_pageGroupItems)
+    {
+        beginResetModel();
+        m_pageGroupItems = std::move(newPageGroupItems);
+        endResetModel();
+    }
+}
+
 QItemSelection PageItemModel::getSelectionImpl(std::function<bool (const PageGroupItem::GroupItem&)> filter) const
 {
     QItemSelection result;
@@ -235,5 +330,50 @@ QString PageItemModel::getGroupNameFromDocument(int index) const
     return fileInfo.fileName();
 }
 
+void PageItemModel::updateItemCaptionAndTags(PageGroupItem& item) const
+{
+    std::set<int> documentIndices = item.getDocumentIndices();
+    const size_t pageCount = item.groups.size();
+
+    if (documentIndices.size() == 1)
+    {
+        pdf::PDFClosedIntervalSet pageSet;
+        for (const auto& groupItem : item.groups)
+        {
+            pageSet.addInterval(groupItem.pageIndex, groupItem.pageIndex);
+        }
+
+        item.groupName = getGroupNameFromDocument(*documentIndices.begin());
+        item.pagesCaption = pageSet.toText(true);
+    }
+    else
+    {
+        item.groupName = tr("Document collection");
+        item.pagesCaption = tr("Page Count: %1").arg(item.groups.size());
+    }
+
+    item.tags.clear();
+    if (pageCount > 1)
+    {
+        item.tags << QString("#00CC00@+%1").arg(pageCount - 1);
+    }
+    if (documentIndices.size() > 1)
+    {
+        item.tags << QString("#BBBB00@Collection");
+    }
+}
+
+std::set<int> PageGroupItem::getDocumentIndices() const
+{
+    std::set<int> result;
+
+    for (const auto& groupItem : groups)
+    {
+        result.insert(groupItem.documentIndex);
+    }
+
+    return result;
+}
+
 
 }   // namespace pdfdocpage
diff --git a/Pdf4QtDocPageOrganizer/pageitemmodel.h b/Pdf4QtDocPageOrganizer/pageitemmodel.h
index 570d4bc..95876b8 100644
--- a/Pdf4QtDocPageOrganizer/pageitemmodel.h
+++ b/Pdf4QtDocPageOrganizer/pageitemmodel.h
@@ -34,6 +34,8 @@ struct PageGroupItem
 
     struct GroupItem
     {
+        auto operator<=>(const GroupItem&) const = default;
+
         int documentIndex = 0;
         pdf::PDFInteger pageIndex;
         QSizeF rotatedPageDimensionsMM;
@@ -41,7 +43,11 @@ struct PageGroupItem
 
     std::vector<GroupItem> groups;
 
+    auto operator<=>(const PageGroupItem&) const = default;
+
     bool isGrouped() const { return groups.size() > 1; }
+
+    std::set<int> getDocumentIndices() const;
 };
 
 struct DocumentItem
@@ -77,21 +83,35 @@ public:
     /// \param index Index
     const PageGroupItem* getItem(const QModelIndex& index) const;
 
+    /// Returns item at a given index. If item doesn't exist,
+    /// then nullptr is returned.
+    /// \param index Index
+    PageGroupItem* getItem(const QModelIndex& index);
+
     ///  Returns true, if grouped item exists in the indices
     bool isGrouped(const QModelIndexList& indices) const;
 
+    /// Returns true, if trash bin is empty
+    bool isTrashBinEmpty() const { return m_trashBin.empty(); }
+
     QItemSelection getSelectionEven() const;
     QItemSelection getSelectionOdd() const;
     QItemSelection getSelectionPortrait() const;
     QItemSelection getSelectionLandscape() const;
 
+    void group(const QModelIndexList& list);
+    void ungroup(const QModelIndexList& list);
+
 private:
     void createDocumentGroup(int index);
     QString getGroupNameFromDocument(int index) const;
+    void updateItemCaptionAndTags(PageGroupItem& item) const;
+
     QItemSelection getSelectionImpl(std::function<bool(const PageGroupItem::GroupItem&)> filter) const;
 
     std::vector<PageGroupItem> m_pageGroupItems;
     std::map<int, DocumentItem> m_documents;
+    std::vector<PageGroupItem> m_trashBin;
 };
 
 }   // namespace pdfdocpage