You may want to see this example

http://doc.qt.io/qt-5/qtwidgets-dialogs-configdialog-example.html

Yes, you are right it will work only one timer because, itemActivated(QTreeWidgetItem*,int), the second parameter is column id. So this will be same for the entire column.

One way to do is that set some information to QTreeWidgetItem and in myslot use this information to call stackedWidget methods.

    QTreeWidgetItem *s = new QTreeWidgetItem();
// set data
    s->setData(0, Qt::UserRole, QVariant("1"));
 
// obtain data   
    QVariant data = s->data(0, Qt::UserRole);

the signal and slot parameter does not match. Try to write your own slot then call stackwidget methods.

example :

connect(ui->treeWidget,SIGNAL(itemActivated(QTreeWidgetItem*,int)), this, SLOT(myslot(QTreeWidgetItem*,int)));

in my slot:
void management_menu::mySlot(QTreeWidgetItem*,int index) 
{
     ui->stackedWidget->setCurrentIndex(index);
}

This should work.