While it is easiest to just let butter soften at room temperature, sometimes you just don’t have time. Such as when a child “suddenly remembers” they were supposed to bring cookies to class the next day.
I do not recommend using a microwave, as it is way too easy to skip softening and go straight to melting.
The trick is to grate it. Grating, even frozen butter, gives it a lot more surface area causing it to warm to room temperature quite quickly. If you are concerned about the amount of butter sticking to the grater, just grate in a tiny bit extra.