Soloing a Channel dimms all other Channel with a specific amount i.e. -20dB. This should make EQing of Signals easyer in relationship to the mix.
It shoud help to set the proper amount of Boost and to find room in the Frequancy Spectrum of the whole Mix. Also this should prevent frequency masking of individual Signals.
The configurable dim amount could be set in the Preferences / Mixing Page.