Did you try to determine why they don't appear ?

Yes, in another project.
QGraphicsView lays a top of QAbstaractScrollArea, so scroll bars appears there out of a box. But it requires a few lines of code to add scrolling by drag a scene.
This time I needed QML way.

@Chris-Kawa Hi..
Ok, we have one model , we are continuously appending data, on that time scroll will be always at bottom, even if we scroll to top , it will come back to bottom, until wee stop appending.
void CustomeTableView::createTabel(QString thText)
{
if(modelList.count()<=25000)
{

modelList.append(thText); numRows = modelList.count(); for (int row = 0; row < numRows; row++) { for (int column = 0; column < numColumns; column++) { QStandardItem *item = new QStandardItem(modelList[row]); fsModel->setItem(row, column, item); } } }

}

@M4RZB4Ni
Hi its all in here
http://doc.qt.io/qt-5/qscrollbar.html#details
But connecting to a random widget will do nothing.

IF u have this case,
user click on Tab
In tab there are many widget so he need to scroll to see last of them, then u just use
a scroll area and put all stuff inside. then it will just work. ScrollArea have scrollbars.
U can control if both horz and vert or just horz.