Is Dark Energy a Constant Strength Through Time?

Dark energy doesn't get less dense as the universe expands, because it's an aspect of space itself. And so proportionally, it grows to be a larger fraction of the energy budget of the universe. But we still don't know what caused in the initial inflation, right? The Big Bang. That could have been also dark energy, but instead you're assigning it to something else,. Or it could have been dark energy that was changing.