This is the visual definition icon responsible for specifying how gridded wind vector data is displayed. It controls features such as wind arrows and wind flags. Note that Metview will automatically interpret certain pairs of meteorological parameters as vector components, for example U/V and 10U/10V - the Grib Vectors icon can be used to ask for other fields to be plotted as vectors.
The macro language equivalent is mwind().
The Wind Plotting Editor
All of the parameters in this editor come directly from Magics, and are documented on the wind plotting reference page