Unify v1.3.x introduced a built-in Stereo Gain plug-in, which simply allows you to boost or cut the amplitude of stereo signals. It is mainly intended to be used inside ComboBox instances, but can also be used in any audio-effect slot in Unify.
The user interface consists of two gain knobs (one for the Left stereo channel, one for Right) and a checkbox in the middle (normally checked) to link the two, ensuring they are always at the exact same value.
Each gain knob has a range from -48 dB (effectively infinite attenuation) to +12 dB (gain), and defaults to the 0 dB position (pass-through; neither gain nor attenuation).