I do not know whether the keystroke shortcut exists; haven’t tried it. But if it is, you’ll need to be absolutely sure (that Blender is absolutely sure…) which node is being referred-to. Seems to me that a right-click approach would be more suitable (if you actually have a choice) for that reason alone.
Interesting. I just tested it and found out it does work and Blender knows which node you’re trying to animate based on where your mouse cursor is at the time you press the I key. This way, you can animate pretty much anything, even individual colors of an RGB curve over time. However, it didn’t seem to work with the above mentioned nodes - Scale and Translate - I don’t know why. It does work in the compositing nodes nicely though. On the contrary, I wasn’t aware of the right-click option, thanks for that.