This option is available in the premium version of the plugin.
This advanced option gives you the power of specifying your own labels for the filtering parameters that appear in the url string of the filtered page address. For example, if you wish to remove the native ” pa_” prefix from the product attribute filters’ labels in the url strings and want to change “pa_sizes” into “sizes”, you can do it here.
Be careful not to assign the parameter names that are reserved by the WordPress itself, Woocommerce, or any of the plugins that are running on your site. Doing so will result in unpredictable filters behavior and other conflicts and errors.