Selecting "the whole body" is not possible.

Poser figures consist of a whole set of individual parts, called "actors".

The entire geometry would be a "Uni-Mesh". Something that Poser cannot do so easily.

Here is the source code of a script that creates a unimesh from Poser figures, which can be further processed in Blender, for example, and the result used as a Poser morph.

https://adp.spdns.org/#ObjImExport

There are some other scripts that might be interesting if you want to get into Poser Python.

https://adp.spdns.org

There is also some discussion in the Python area. This one is the second part: https://www.renderosity.com/forums/threads/2955142

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