As specifically described in DMsG text description of the extension - it expects the spell or power as normally defined in FGU to be defined in order to enable the pull down in polymorphism. It must find that exact keyword in there. Nor will it work with that spell once enabled - only the polymorphism subwindow functions will do that. That’s why I specifically mentioned it and showed it in video.
No idea what the extension your talking about is, but it’s not polymorphism and if not adding the expected keyword in spell power area of actions tab as described in text and shown in video it obviously will not do anything with my stuff.
That’s all guessing based on your short explanation as I’ve only used and verified this extension under the ones in my signature. And while I’ve seen someone say it worked with other extensions - which is great and I’m happy for them - you will never hear me claim it does unless I personally run with it.
Pretty sure other extension developers will tell you same thing about their extensions and unknown (like mine) running with there stuff.