In the meantime I may have found a solution myself:

Can I handle it this way ?

Would it be more efficient to add a filter in MouseEnterElement and remove it in MouseLeaveElement?

public bool PreFilterMessage( ref Message m )
        {
            const int WM_LBUTTONDBLCLK = 515;

            if (m.Msg == WM_LBUTTONDBLCLK)
            {
                Console.WriteLine("Left Mouse double click");

                Point     screenPoint = Cursor.Position;
                RibbonTab tab         = _mgr.RibbonTabFromPoint(screenPoint);
                UIElement uiElem      = _mgr.UIElementFromPoint(screenPoint);

                if (uiElem?.Parent is RibbonTabItemUIElement)
                {
                    Console.WriteLine($"Mouse inside of {tab.Caption}");

                    return true;
                }
            }

            return false; // Not Handled
        }

Hi Andrew,

thanks for your help.

Did you probably forget to attach the example? :-)

Michael