Ahh - Yes those Pan parameters are for each sample in the Sample type Engine. Even if it was possible to modulate them, then it would'nt help on the other Engine types. And you would have to modulate all the used samples individually. But i think it should be possible to modulate them anyway. Don't know why we can't,. I have wondered about that. Perhaps it's an oversight from Arturia or because they are in the edit mode. But then again - it is possible to automate them in a DAW.
When you run Filters in Parallel, then you can route Each Engine individually to each filter. Then you can modulate the Filter Pans independent pr Engine > Filter and also > individual FX lines. So unless you have to use the two main filters in seriel mode, then it should be easy to do what you wan't. That's why i mentioned Seriel in my first post.
Even using the Stereo panner can work When you have the Filter routing set to Split. Then the main filters also does'nt run in Serie.
EDIT: Even when running the main Filters in seriel mode, then if you have Filter 2 set to normal stereo (Center), then you can modulate Filter 1 Pan free. Actually you can allways do that, but when moving Filter 2s pan, then it will affect what come from Filter 1. So if Filter 1 is panned fully left and Filter 2 is panned fully right, then you hear no output from Filter 1. But then again, - sometimes it can be a matter of using volumes to mix the sound, and then just not turn Filter 2 Pan fully to one side. EDIT END