Well not on the list, so wonder how it opens it. If right click the .dds file and select properties by clicking the change button will tell you it is associated with it, but here can only change it to another program. Default Programs area in your last 2 pics is only place i know unless find it in the registry and edit it or uninstall the game and reinstall. For one Windows Photo Viewer is really no longer used in Windows 10, Photos is new one, either you restored it or came over from the existing operating system.
Sorry this is all i know. Did i have the reasons correct on why you have to open a .dds file to begin with or is it opening and you do not want it to, not much else is explained here.