True bi-lateral symmetry requires sign changes on X translations and Y & Z rotations (in the simplest form that relates to human figures, at least). Poser knows how to do that, but cannot do so for morphs unless they contain a paired L/R suffix, so it can't tell that SideSideAll is a master channel for z-rotations. If you were to bake those morphforms (a common name for master channels) out to the individual limb actor rotations, then Poser's symmetry functions could work with them. Unfortunately, there is no (simple) way to uncook an egg or replace a set of common limb rotations back into a morphform that controls them.

Looking through the free stuff and marketplace came up with this: NetherWorks' PoseWriter Panel as the only readily available option for morph symmetry. I have written such scripts for my highly customised V4 figure, without the UI, though, and there is a great deal of customisation required to identify trunk and limb control morphforms (master parameters) which are subject to symmetry transfers. The Giant Octopus is certainly a prime candidate for such treatment, but my script would take significant work to bring up to the same standard and general figure applicability as NetherWorks' offering, so I'll leave it at that.

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