Not familiar with using Geometric_Edge but if its a setting in the Material room maybe one of the available material manager systems could help. I've adapted one of my scripts to change this param on the current active figure - if you don't get any better responses it might be worth a test

import poser
scene = poser.Scene()
RenderEngine = scene.CurrentRenderEngine()
CurMaterials = scene.CurrentFigure().Materials()

NewValue = poser.DialogSimple.AskFloat("Enter Geometric edge value or cancel to skip") 

if NewValue:

    for mat in CurMaterials:

        rootNode = mat.ShaderTree().RendererRootNode(RenderEngine)
        input = rootNode.InputByInternalName("Geometry_Edge_Dist")

        if input:
            print "Changing " + mat.Name() + " Geometric Edge to ", NewValue
            input.SetFloat(NewValue)

    print "nScript finished. Hit x on top right of window to close"