To add a second delegate to a row in QTreeView, you need to create a custom delegate that can handle both types of data and use it for the specific rows where you want to show the second delegate.

Here’s an example:

#include <QtWidgets>

class CustomDelegate : public QStyledItemDelegate {
public:
    CustomDelegate(QObject *parent = nullptr) : QStyledItemDelegate(parent) {}

    void paint(QPainter *painter, const QStyleOptionViewItem &option,
               const QModelIndex &index) const override {
        // Check if this is the row where we want to use the second delegate
        if (index.row() == 1 && index.column() == 0) {
            // Use the second delegate for this row/column
            m_delegate2->paint(painter, option, index);
        } else {
            // Use the default delegate for all other cases
            QStyledItemDelegate::paint(painter, option, index);
        }
    }

    QWidget *createEditor(QWidget *parent, const QStyleOptionViewItem &option,
                          const QModelIndex &index) const override {
        // Check if this is the row where we want to use the second delegate
        if (index.row() == 1 && index.column() == 0) {
            // Use the second delegate for this row/column
            return m_delegate2->createEditor(parent, option, index);
        } else {
            // Use the default delegate for all other cases
            return QStyledItemDelegate::createEditor(parent, option, index);
        }
    }

    void setEditorData(QWidget *editor, const QModelIndex &index) const override {
        // Check if this is the row where we want to use the second delegate
        if (index.row() == 1 && index.column() == 0) {
            // Use the second delegate for this row/column
            m_delegate2->setEditorData(editor, index);
        } else {
            // Use the default delegate for all other cases
            QStyledItemDelegate::setEditorData(editor, index);
        }
    }

    void setModelData(QWidget *editor, QAbstractItemModel *model,
                      const QModelIndex &index) const override {
        // Check if this is the row where we want to use the second delegate
        if (index.row() == 1 && index.column() == 0) {
            // Use the second delegate for this row/column
            m_delegate2->setModelData(editor, model, index);
        } else {
            // Use the default delegate for all other cases
            QStyledItemDelegate::setModelData(editor, model, index);
        }
    }

    QSize sizeHint(const QStyleOptionViewItem &option,
                   const QModelIndex &index) const override {
        // Check if this is the row where we want to use the second delegate
        if (index.row() == 1 && index.column() == 0) {
            // Use the second delegate for this row/column
            return m_delegate2->sizeHint(option, index);
        } else {
            // Use the default delegate for all other cases
            return QStyledItemDelegate::sizeHint(option, index);
        }
    }

    void initSecondDelegate(QAbstractItemDelegate *delegate) { m_delegate2 = delegate; }

private:
    QAbstractItemDelegate *m_delegate2 = nullptr;
};

int main(int argc, char *argv[]) {
    QApplication app(argc, argv);

    QStandardItemModel model(3, 1);

    QTreeView treeView;
    CustomDelegate customDelegate;
    treeView.setItemDelegate(&customDelegate);

    QLineEdit lineEdit;
    customDelegate.initSecondDelegate(lineEdit.lineEdit()->itemDelegate());
    
    treeView.setModel(&model);
    treeView.show();

    return app.exec();
}

In this example, we create a CustomDelegate that checks if the current index is in the row where we want to use the second delegate (row == 1 && column == 0). If it is, we call the corresponding methods on the second delegate; otherwise, we use the default delegate.

To use a custom delegate for a specific row, you need to initialize it with the desired delegate. In our case, we initialize it with a QLineEdit’s item delegate using lineEdit()->itemDelegate().

Note that this example only adds a second delegate to one specific row and column combination (row == 1 && column == 0). If you need to add multiple custom delegates or more complex logic for selecting which delegate to use based on data or other criteria, you will need to modify this code accordingly.