Regrettably, WXSolution does not provide weather tags for doing the displays for a WXS-trends-inc.php, so it was omitted from the WXS-plugin for that reason. WeatherLink software also is missing those variables, so it, too, has no trends page.
Weather-Display, Cumulus (and CumulusMX), and Meteohub do provide them, as does the Ambientweather.net plugin.