Well, that would only work if you had a visible category drop-down filter. The “getStateURL” is used to return the current state of the filters.
You could perhaps try to make a category drop down filter, then select the required category, then do the “getStateURL” command. After that, don’t remove the filter from the configuration, but only hide it. Then the filter is still active, but invisible, so entering the URL the filter is still in use.