As there are two windows now (Flow and Summary), common commands such as Run, Customized run, Clear and About were moved to the new toolbar in Visual Studio:
Runtime Flow toolbar
The new toolbar also adds commands to open the Flow and Summary windows. The previous command to open the Runtime Flow window in the Other Windows menu is now removed. When monitoring is started with both windows closed, the Runtime Flow window is opened automatically.
Runtime Flow blog (Understanding a control flow in a running .NET application) 