Describe your enhancement

We should add the equivalent of a quarts fiber: a cable to transfer just energy. that will allow making subnets without using a relay for multi-machine crafts, but won't add too much complexity.

For example, I made this quick setup to smelt stuff in parallel by using a relay. If we had energy cables, it would make this a bit more intuitive and simple.

The relay can do it in 2 button clicks away. No need to introduce duplicate functionality this way.

I don't get it, the relay can also do it in 1 block? What complexity do you mean?

The relay is for more complex use cases: sharing storage/patterns. But if you need a small separate network, an energy cable is a lot better for that. No extra buttons, no extra configuration, just a way to power isolated components.