If I understand your text correctly (English is not my native language) then you describe pretty much what the script "ImExport.py" does.

The current Poser figure, which consists of individual "Actors", is combined into a Unimesh and exported (morphed and posed) as an OBJ file.

This Unimesh can be edited in Blender with all the tools available there. Afterwards, from Blender, it is saved again as an OBJ file (necessarily under a different name).

The script in Poser takes the two saved meshes (OBJ files saved from Poser and Blender) and creates a difference from them. The result, the difference, is the "Unimesh Morph". The Unimesh Morph is then decomposed and saved into the affected Actors as a Morph.

What did I get wrong?

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