You can use PitchFlex algorithm to do this.
Note that PitchFlex is a stereo effect. Therefore, if you just want one pitch, you may set the Pitch Mix to A10+B0. Then you can just set the pitch drop for the voice A.
For example, if you want to drop a whole step, you need to set: Mix = 100, Pitch Mix to A10+B0, Heel A = -M2, Toe A = -M2, Filter = 0.
If you have an expression pedal connected, you can also use this as a whammy effect. Just change the Heel and the Toe to whatever pitch you want. If you want stereo effect, please change the Pitch Mix, Heel B, and Toe B accordingly.