@SergeyK12
Are you aware that in a QStandardItemModel you can create a parent-child hierarchy? E.g. start from https://doc.qt.io/qt-6/qstandarditemmodel.html#details and QStandardItemModel::insertRow(int row, const QModelIndex &parent = QModelIndex()) etc.

So why don't you store your model like that if it's hierarchical?

Unless you mean you start with a QStandardItemModel which is flat and multi-column like the first one, for whatever reason, and want to display that in the second way. For that yes a proxy like yours would be good.

@VRonin said in Treeview remove row:

if(parent.isValid() && parent.column()>0) return 0; const TreeItem *parentItem = getItem(parent); return parentItem ? parentItem->childCount() : 0;

All good now. Thank you very much, sir.