One of the novelties of the latest version of gvSIG Online is that apart from the typical types of legend (unique symbol, unique values, expressions or intervals) we can create custom legends through the SLD format.

Thanks to this format we can load symbologies that we have previously created in a layer in a Desktop GIS on the one hand, and on the other hand we can apply symbology of different types to apply heat maps, patterns, transformation functions …

You will be able to consult all these options in the Geoserver documentation, and in this video you will be able to see how it works and some practical cases: