It seems like there is no way of getting a filtered point cloud output from the Realsense TOP using a Realsense D455 on Windows 10 Pro, TD build 2021.13610.
When setting the output of the TOP to point cloud the filter tab is disabled.
In this thread I was advised to try adding another Realsense TOP outputting depth, as that might affect the point cloud output. I have tried depth, raw depth & depth aligned to color, but the filter settings in these TOPs does not affect the output of the point cloud TOP.
On Discord, I heard that alphamoonbase.berlin had experienced that settings made in RealsenseViewer for the L515 would persist when opening TouchDesigner. I have tested this, but it is not the case for the D455.
I am not sure, but it could be related to this: Realsense TOP: Pointcloud filter not working with ColorToDepth