I added the [JsonIgnore] to the OnValueChanged property in the DropdownSetting class.
Changes to the csproj were because my system wasn't recognizing the D: references to Newtonsoft.Json, and UnityEngine.CoreModule dlls. Also shows conflict that I don't need the UnityEngine.dll as it has a similar class to UE.CoreModule.
I added the [JsonIgnore] to the OnValueChanged property in the DropdownSetting class. Changes to the csproj were because my system wasn't recognizing the D: references to Newtonsoft.Json, and UnityEngine.CoreModule dlls. Also shows conflict that I don't need the UnityEngine.dll as it has a similar class to UE.CoreModule.