One field where Djay is missing in my opinion is the lack of Filter FX, We have really crazy stuff like Crossfader FX so it’s surprising to me that we don’t have such a simple thing as that.
Even controllers that have this feature built in never have full functionality in Djay Pro, it is either switched off as in Traktor Kontrol S3, or it is a cheated solution like running your FX1 together with a filter like in Mixon 4.
This is far from ideal, and using one of the 3 FX slots permanently just for a filter is very limiting, especially as we have no easy option to quickly switch between a few favourite effects on the fly without having to click, scroll through dozens of effects (at least on Windows, I don’t know how it looks on other platforms).
PAD FX controls FX and Filter at the same time but it’s completely useless for controller users so I think adding a fully fledged filter effect mode would be a great addition.
Thanks! 
