DJM-A9: I wish the FX buttons were toggles

When I bought this mixer and I looked at the layout, I thought I'd be able to turn the FX target buttons on and off independently. E.g. I can turn on 1 and 3 for those decks to have FX applied, and have them not applied to 2 and 4. And then be able to press 1, and have FX only apply to 3 (although the tail of the FX should play out nicely on decks I turn off).

I was surprised to not be able to do this. I don't if it's possible in an update, but I would like it.