There is an Amplifier tool/brush in SpectralLayers. But to de-amplify you have to select the area you want to “dim” then go to Process->Amplitude->Gain… In Photoshop you have Dodge and Burn tools. So De-Amplifier would be great to have. Intuitively I tried using Amplifier with Alt held to de-amplify, but it didn’t work.
So either another tool to de-amplify, or option to de-amplify with Amplifier tool with modifier key (Alt, for example) held.
P.S. Maybe I’m again missing it somewhere.