P5 nodes are tricky for any external app to handle because the complete shader tree does not actually reside in memory all the time so there is no way to edit or modify it on the fly by scripts or MAT Poses. The only part that P5 keeps in memory is the Poser Surface Node. The rest of the tree is dynamically generated at render time, and when making changes in the material room. This is the reason that most shaders don't show any effect other than basic color in the preview window. It is also why it sometimes "appears" that poser is retaining old material settings when in actuality it is just not being properly instructed by the MAT pose. There IS a way to force P5 to update the whole tree on the fly, but that's a complicated story best left to a tutorial.