I have not been able to figure how to take 1 FX bus send and route it to multiple FX engines, inversely you cant route a Aux to the FX engine and have it continue to return in a FX return channel strip.
I will add that you can assign FX sends and returns to DCAs.
I used to route a single FX send to multiple FX effects with an X32. I did this with vocal effects for example and it provided a single fader (FX send) to quickly pull the effects out while still giving individual volume control over each effect using the returns.
Once I realize I could assign the vocal FX channels to a DCA, I have my single fader back for volume control.