You can only adjust brightness for individual modes in the show builder. In modes and lists, the brightness and saturation are global settings and we do not have a way to save them per mode. Most people would probably be confused if they saved a mode when the brightness happened to be low, and consequently appear dimmer than their other modes.

There is one mode, “lantern” (p1m4), that has brightness as its second adjust. You can control the color and brightness, and even save a series of them at various brightnesses to create the appearance of a fade-in or fade-out effect.