@zangchunyu: The problem is that neither psa export nor ActorX importer doesn't support time arrays in the core, unlike gltf. Reworking the whole thing would take a lot of time, considering that I'm not fluent in 3ds max scripting. I can only provide a workaround with linear interpolated intermediate keys, but that's not totally accurate. It's better to use gltf export, where only actual keys are loaded on timeline according to time arrays and users can interpolate them however they want. Anyway, "materials" build has this workaround now and you can use attached updated importer, which can import scale keys from psa.
Thanks for the detailed explanation of the material build.
According to my testing by far, everything works just GREAT for the scaling keys.
Btw, the special normal data works WONDERFUL also, maybe we could just update this version of actorXImporter.ms as the "recommended" by default.
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Update: there's a small bug that every anim segments are reproducing the first segment's scale track. for example, if the psa animSet contains anim A,B,C while A has scale keys then B and C will also have the same scale tracks. If A doesn't have scale keys while C does, then C will not show the scale anims in 3D max. I'm not sure whether this copying was happened in the process of exporting from UViewer or in importing into 3DMax.