Waterfall sink does not have 'Control panel' in the 'Config' tab

Hi

The problem is that waterfall sink does not have the option 'Control panel' in the 'Config' tab.

One should be able to toggle the control panel on and off.

The control panel can be seen e.g. in the figure at

https://wiki.gnuradio.org/index.php/QT_GUI_Waterfall_Sink

This problem is similar to

https://stackoverflow.com/questions/69413916/how-to-expose-the-control-panel-of-the-qt-gui-time-sink

I have Ubuntu 20.04.4 LTS and GRC 3.8.1.0 (Python 3.8.10)

cheers, Kimmo