In the docs:

void QTableWidget::cellEntered(int row, int column)
This signal is emitted when the mouse cursor enters a cell. The cell is specified by row and column.

This signal is only emitted when mouseTracking is turned on, or when a mouse button is pressed while moving into an item.

This function was introduced in Qt 4.1.

BUT the signal is also emitted by Mousewheel unless when you say "mouse button is pressed" you also mean the mousewheel

Check the last post on the forum topic: https://forum.qt.io/topic/9692/how-to-drag-drop-rows-within-qtablewidget/7