QStackedWidget *stack = new QStackedWidget();

QComboBox *comboBox = new QComboBox();

comboBox->addItems({"A", "B", "C"});

stack->addWidget(comboBox); // index 0

stack->addWidget(new QWidget()); // 空白 widget, index 1

tableWidget->setCellWidget(row, col, stack);

// 显示 comboBox

stack->setCurrentIndex(0);

// 隐藏 comboBox（显示空白）

stack->setCurrentIndex(1);