I instelled windows10 ,UE4.13 , VS2015 communit , DXSDK2010 , win10SDK and SimplygonSDKSetupReleasex64_8.1.6147.
I registed simplygon account and download a license of personal free , enter the license into simplygon for ue4 installer
and then, I start UEeditor.
it shows “LogSimplygon:Warning: Failed to initialize Simplygon. Error: 0.” in output log. In LOD setting, it still shows “auto mesh reduction is unavailable …”
BTW, www.simplygon.com/download → simplygon integrations → unreal engine(SDK only) is empty, while Unity not.
Follow the video provided by Simplygon on how to integrate into Unreal Engine 4. The field you are pointing out is empty because Simplygon is now free to use.