Carl, it is not currently in Project Online and according to the Office 365 Roadmap (http://fasttrack.microsoft.com/roadmap) it is rolling out to Project Online, which I have and is available for me. You should see it soon if you don’t yet. Project 2016 desktop has multiple timelines. I would assume it is available in Project Server 2016 (on premise) but do not know the status. Hope that helps…