Dark energy is a bandaid that is needed to close the universal energy balance because of problems created by the relative reference assumption, used to explain how we see the universe.
When we look out at the universe, the only sense we can use is the sense of sight. We cannot hear, taste, touch or smell the universe. However, we can see various energy emissions and use that to judge the universe. We cannot use the sense of touch to directly ascertain things like momentum and inertia.
This single sense default situation, for astral physics, creates a problem due to the lack of checks and balances with the other four senses. We can see a star by its emissions, but we cannot touch it to know other properties for a check and balance. We see the material and inertial universe only through its light emissions mask. This can be deceptive.
As an example, say you were a man at a train station waiting for your train. You can see the train arriving at the station. If we only use the sense of sight, the man can assume relative motion. He can say that the arriving train is stationary, and the man is in motion moving toward the train.
Although this will satisfy the eyes, it will not satisfy the needs of an good energy balance, since a moving train has more mass and kinetic energy, than a moving man, if both use the same velocity.
The man who uses only his eyes to assume he is moving in relative motion with the train, will violate energy conservation by under estimating the total system energy; train's actual momentum based on its fuel consumption which is quantifiable. With the energy balance off, we now we will need a bandaid to make up for the extra energy, that is not evident to the man's sense of sight. Dark energy is an bandaid, due to the poor energy balance, created by the one sense, relative reference assumption.
Dark energy has never been seen in any lab to know it is real. It is needed to close the energy balance problem created by visual only, relative reference.