Fold3 has a box you can check to add a Gold Star to a WWII fallen. It is used for any serviceman or woman who died while the country was actively involved in combat, regardless of the cause of death.
Together We Served also has a Gold Star designation in the Unofficial Badges section of the the Service History. TWS follows the more accurate practice of associating the Gold Star with Next of Kin, not the fallen. So for TWS Profiles, do not mark the Gold Star award for the fallen (unless they are next of kin to another fallen). I previously gave out the wrong instructions about this.