Whilst I don’t have the Numark Platinum FX,
I have mapped my Prime Go to do this as well.
Having a look at an image of the Platinum FX, You could go into the Midi Learn setting and map Shift + Headphone Cue to Toggle Neural Mix EQ for each deck,
So Deck 1 Shift + Headphone Cue and then do the same for Deck 2.
And when you want to swap back to regular EQ just press the same buttons.
