Как передать значение из реестра

У меня есть виджет строкового поля. Как сделать, чтобы сохранялся текст этой строки и передавался в реестр, чтобы потом можно было загрузить сохранённый текст данной строки.

mainwindow.h:

#ifndef MAINWINDOW_H
#define MAINWINDOW_H
#include <QMainWindow>
#include <QSettings>
#include "counter2.h"
namespace Ui {
class MainWindow;
}
class MainWindow : public QMainWindow
{
    Q_OBJECT
public:
    explicit MainWindow(QWidget *parent = nullptr);
    ~MainWindow();
private:
    Ui::MainWindow* ui;
    counter2*       counter_2;
    counter2*       counter_3;
    QSettings*      settings;
public:
    void save();
    void load();

//signals:
//    void toggleToCounter2();
private slots:
        //Diclaration slots'
    void cleanLines();
    void cleanAmounters();
    void cleanAll();
    void toggleCounter3();
    void toggleCounter4();
    void toggleCounter5();
    void toggleCounter6();
    void toggleWindow2();
    void toggleWindow3();
};
#endif // MAINWINDOW_H

mainwindow.cpp:

#include "mainwindow.h"
#include "ui_mainwindow.h"
#include "counter2.h"
MainWindow::MainWindow(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::MainWindow)
{
    ui->setupUi(this);
    counter_2 = new counter2();
    counter_3 = new counter2();
    settings = new QSettings("SimpleStudio", "Counter", this);
    //Diclaration variables & QObject::connect
    connect(counter_2, &counter2::toggleToCounter1,
            this,      &MainWindow::show);
    connect(counter_3, &counter2::toggleToCounter1,
            this,      &MainWindow::show);
    connect(counter_2, &counter2::toggleToCounter3,
            this,      &MainWindow::toggleWindow3);
    QObject::connect(ui->toggleButton2, SIGNAL(clicked()),
                      this,     SLOT(toggleWindow2()));
    QObject::connect(ui->toggleButton3, SIGNAL(clicked()),
                      this,     SLOT(toggleWindow3()));
    QObject::connect(ui->cleanLines, SIGNAL(clicked()),
                     this,           SLOT(cleanLines()));
    QObject::connect(ui->cleanAmounts, SIGNAL(clicked()),
                     this,             SLOT(cleanAmounters()));
    QObject::connect(ui->cleanAll, SIGNAL(clicked()),
                     this,         SLOT(cleanAll()));
    QObject::connect(ui->checkBox3, SIGNAL(clicked()),
                     this,          SLOT(toggleCounter3()));
    QObject::connect(ui->checkBox4, SIGNAL(clicked()),
                     this,          SLOT(toggleCounter4()));
    QObject::connect(ui->checkBox5, SIGNAL(clicked()),
                     this,          SLOT(toggleCounter5()));
    QObject::connect(ui->checkBox6, SIGNAL(clicked()),
                     this,          SLOT(toggleCounter6()));
//    load();
}

MainWindow::~MainWindow()
{
    delete ui;
    save();
}
//Discription slots'
void MainWindow::save() {
    ui->nameCounter1->setText(settings->setValue("nameString1", ui->nameCounter1->text()));
}
void MainWindow::load() {
    ui->nameCounter1->setText(settings->value("nameString1").toString());
}
void MainWindow::cleanLines() {
    ui->nameCounter1->clear();
    ui->nameCounter2->clear();
    ui->nameCounter3->clear();
    ui->nameCounter4->clear();
    ui->nameCounter5->clear();
    ui->nameCounter6->clear();
}
void MainWindow::cleanAmounters() {
    ui->amounter1->setValue(0);
    ui->amounter2->setValue(0);
    ui->amounter3->setValue(0);
    ui->amounter4->setValue(0);
    ui->amounter5->setValue(0);
    ui->amounter6->setValue(0);
}
void MainWindow::cleanAll() {
    ui->nameCounterTop->clear();
    ui->checkBox3->setChecked(0);
    emit MainWindow::toggleCounter3();
    ui->checkBox4->setChecked(0);
    emit MainWindow::toggleCounter4();
    ui->checkBox5->setChecked(0);
    emit MainWindow::toggleCounter5();
    ui->checkBox6->setChecked(0);
    emit MainWindow::toggleCounter6();
    emit MainWindow::cleanLines();
    emit MainWindow::cleanAmounters();
}
void MainWindow::toggleCounter3(){
    if(!ui->checkBox3->isChecked()) {
        ui->amounter3->setEnabled(0);
        ui->nameCounter3->setEnabled(0);
    } else {
        ui->amounter3->setEnabled(1);
        ui->nameCounter3->setEnabled(1);
    }
}
void MainWindow::toggleCounter4(){
    if(!ui->checkBox4->isChecked()) {
        ui->amounter4->setEnabled(0);
        ui->nameCounter4->setEnabled(0);
    } else {
        ui->amounter4->setEnabled(1);
        ui->nameCounter4->setEnabled(1);
    }
}
void MainWindow::toggleCounter5(){
    if(!ui->checkBox5->isChecked()) {
        ui->amounter5->setEnabled(0);
        ui->nameCounter5->setEnabled(0);
    } else {
        ui->amounter5->setEnabled(1);
        ui->nameCounter5->setEnabled(1);
    }
}
void MainWindow::toggleCounter6(){
    if(!ui->checkBox6->isChecked()) {
        ui->amounter6->setEnabled(0);
        ui->nameCounter6->setEnabled(0);
    } else {
        ui->amounter6->setEnabled(1);
        ui->nameCounter6->setEnabled(1);
    }
}
void MainWindow::toggleWindow2() {
        counter_2->show();
        this->close();
}
void MainWindow::toggleWindow3() {
        counter_3->show();
        this->close();
}
//void counter2::toggleWindow3() {
//    counter_2->close();
//    counter_3->show();
//}

Ошибка: mainwindow.cpp:64: ошибка: reference to type 'const QString' could not bind to an rvalue of type 'void'