I'm currently using the latest build of Blender 2.8 as of this post's timestamp, and I noticed I can't keyframe the viewport visibility parameter (see above) in the Outliner like in 2.79. The render visibility parameter (already yellow/keyframed) works fine.
This error is probably because the feature is not implemented yet, but this whole situation has made me look into other methods of hiding and unhiding objects in my animation. Specifically, I want to know if scaling a mesh or curve object to 0 will remove that object's impact on render time, as if it was never in the scene.
It makes the most sense to just use 2.79 until this new Blender version is finished, but I vaguely recall overhearing once that keyframing this parameter with a large number of objects at a time is not recommended, so it's a good opportunity to explore alternatives.
So does scaling to 0 remove an objects impact on render time? If not, what are some other ways I can animate object visibility (excluding keyframing a material's transparency)?