QWT Curve symbol show/hide

I am able to set set symbol for curve. Is there any option to hide/show or change color when needed? The problem is the only way I could do was setting a "NoSymbol" style to remove symbols, but I understand it is in-efficient as it deletes all the old symbols and create new each time I toggle. Is there a better way to sho or hide curve symbols display after setting only once first time?

There is only one QwtSymbol for each curve - so no: it is not in-efficient to delete/create a new one.
What takes time is to replot the plot, when changing curve parameters. But this is something you can't avoid.

HTH,
Uwe