Photoshop: Video timeline - hide part of a layer I have recently got into Video Timelines with Photoshop CC 2015.

I am trying to make a transition with text. I can rasterize it if needed. I am trying to make it so that only part of the text is showing and the other part is hidden. I want to do this for a transition. How can I do this without any additional layers?
In general, when you use a program as complex as Photoshop, you don't want to fight its idiomatic way of doing things, you want to use it instead.  The idiomatic way of hiding/revealing parts of an image (which, in turn, means parts of a layer or set of layers) is with a mask, which is typically its own layer.  The layering system of Photoshop is a major aspect of its functionality.  Don't fight it or try to not use it.  Learn it, master it, and then use it.