How to know if the new MacBook is charging while turned off?

Solution 1:

Curiously, Mac portables has been designed to be put to sleep instead of shutdown for very long time (I occasionally reboot, but never shutdown my iBook G4, which is from 2004)

So the solution would be using it as how it was designed, put it to sleep, open lid to check.

Yay, that's the USB standard's issue. They should have spec in optional indicator and signaling to the USB connector.

Solution 2:

You will need an adapter but here's a quick, easy, inexpensive solution:

Solution 3:

Sorry to say, but it's not possible to check that without looking on screen. The idea from tjt263 is a good one, but since USB type C is fairly new, there isn't an adapter available for USB-C. I suggest to wait 'til new cables with a charging indicator included are released.