There is no timeline in Visual Studio, there has never been one.
This is a deliberate choice. Blend is the tool of choice for animations. Visual Studio for the basic authoring. Two different audiences according to Microsoft. The hard-core developer will use Visual Studio to build the skeleton UI in Visual Studio. The hard core UX designer will then add the animations and other cool effects in Blend.
If you can do both, you'll have to switch between tools.