addWidget other place than setCentralWidget()

[Oleg]

1. BTW, create all widgets in visual editor, it's much easier.
2. Add layout to your tab

tab->setLayout(new QVBoxLayout());

tab->setLayout(new QVBoxLayout());

To copy to clipboard, switch view to plain text mode 

3. Add QPushButton and QGroupBox to that layout

tab->layout()->addWidget(new QPushButton());
tab->layout()->addWidget(newGB);

tab->layout()->addWidget(new QPushButton());
tab->layout()->addWidget(newGB);

To copy to clipboard, switch view to plain text mode