What to do with unused Logic Level Shifter lanes?

Hi,

I am actually putting some ESPs, Arduinos and Sensors together, so I will need a few logic level bidirectional shifters. I´ve ordered some with 4 lanes, and some with 2x TX & RX.
As I do not need 2x RX TX or all 4 lanes on every shifter, I think about what to do with the empty lanes. Do you connect both sides of them to ground, to ensure "electric noise" does not cause them to shift? Leaving them empty would be nice to fast add some stuff to shift, but if it costs energy, I´d prefer to avoid that.

Only connect the input to ground or supply-voltage. Don't connect anything to the output.

With opamps that have several units in one package, it's extremely important to tie all un-used inputs to a known voltage. Otherwise the random noise on those channels can affect the ones you're using.

Leaving them empty would be nice to fast add some stuff to shift, but if it costs energy, I´d prefer to avoid that.

Leaving them unconnected is the best thing to do because they already have their own built in pull up resistor.
Yes that will "cost energy" the way to reduce that is to unsolder the FETs, but it is a very very small amount of energy you will save, not worth it in my opinion.

I´ve ordered some with 4 lanes, and some with 2x TX & RX.

If they are bi-directional then they don't have a TX and RX.