If you have the cookie here is an example of how you can add it to your CustomCookies on the Location.
foreach (Cookie cookie in response.Cookies)
var version = location.Hub(noVersionCheck: true).ProductVersion();
I have posted an example on branch.qlik.com / github see GitHub - AptkQlik/SDKConnectionWithSenseTicket: Connect with the Qlik Sense .Net SDK using an existing session
I hope this is helps you in what you are looking for.