Hmmmmm been doing some stuff with hands. Thought I might share my findings with you and see what you think.

I've got a fully-loaded (all Morphs++) V4 that I'm using to create my poses. Now, I realise I don't need all the morphs... indeed, they may get in the way, but never-the-less this is the girl I'm "using"... in the nicest possible way, of course.

I decided to try saving a hand pose, which I did by the click on the [ + ] in the hand library, which asks which hand's pose I intend to save. I selected "left" which was the pose I had modified. It then asked for the Save Frames (single frame) and that was it. The thumbnail was a screenshot of my LHand Camera view of the hand.
So far, so cool.

I opened this in Poser File Editor to see how what I had created compared to what I consider the industry standard: Ilons'a Pretty Hands.
Right.

Under  version, it had 7 point something, which I changed to 4.01, which is what Ilona has. I would guess that it makes things more compatible to use an earlier version number.

Then, under each actor, it said rHand, rThumb1 etc, even though I had selected "left". Same as in Ilona's file, so I guess that's what it saves as.

Under channels, Ilona only had rotateX xrot, rotateY yrot and rotateZ zrot. Poser 7 sr3 generated all these other channels: a whole slew of target Geoms fbms and pbms. Well, Ilona didn't have that stuff and so neither shall I so I deleted the lot.

Now, I have tried a hand pose from someone who had left them in. I'm not certain if it's cause-and -ffect but invoking that pose generated a "Information stored in this library entry does not pertain to figures of this type" error. After I took those target Geoms fbms and pbms out in Poser File Editor it posed correctly without the error. Don't think the error in-and-of-itself is a fatal one, but it's annoying and to novice users a bit disconcerting.

Monterey/Mint21.x/Win10 - Blender3.x - PP11.3(cm) - Musescore3.6.2

Wir sind gewohnt, daß die Menschen verhöhnen was sie nicht verstehen
[it is clear that humans have contempt for that which they do not understand] 

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