How to pass data between forms and change them?

Question

Qt

I am making a reminder program like Birthday in QT. I don't understand how to implement "edit" and "add" buttons for tasks. By pressing the "add" button, a second form opens in which I enter the task, I press OK and it is transferred to the main form and displayed on the screen. And by pressing the "change" button, the selected object (or a pointer to it, I don't know how to do it all) is also transferred to the second form and edited there, after which we return it to the main form. mainwindow.cpp

void MainWindow::on_pushButton_add_clicked()
{   Script stakan;
    Dialog *add = new Dialog(stakan, this);
    add->exec();
    Script stakanadd = add->stakan;
    if (add->g==true){
        korobka.append(stakan);
 
    }
    else {
 
    }
 
    add->deleteLater();
    korobka.append(stakan);
 
 
}
 
void MainWindow::on_pushButton_edit_clicked()
{
    Script stk;
    stk.SetText(ui->Today->currentItem()->text());
 
    QVariant data=ui->Today->currentItem()->data(Qt::UserRole);
    stk.setData(data.toDate());
 
    Dialog *sohr = new Dialog(stk, this);
    sohr->exec();
    Script stakanedit = sohr->stakan;
    if (sohr->g==true){
        korobka.append(stakanedit);
    }
    else {
 
    }
 
    sohr->deleteLater();
    korobka.append(stakanedit);
}

dialog.cpp

void Dialog::on_button_changeValue_accepted()
{
 
    g=true;
    Dialog::close();
 
 
}
void Dialog::on_button_changeValue_rejected()
{
    g=false;
    Dialog::close();
}

stakan is an object of class Script

class Script
{
public:
    Script();
    void SetText(const QString &str);
    QString GetText();
 
 
 
    QDate getData() const;
    void setData(const QDate &value);
 
private:
    QString text;
    QDate data;
};