Various mods by zahar0z

Well, I don't know, all the default animations were exported through gr2 maya, and there are two possibilities here: either it was made "incorrectly" from the game's point of view, most likely because the disappearance effect is not visible in Granny Viewer, or you need to experiment with the export settings. Or, could you use some animation with the model and this effect? Maybe it will be possible to make it work.

It's quite possible that something wasn't checked in the export settings.
There's also a theory that the object hierarchy might be breaking during import through the editor. I haven't checked this, but in theory, even a correctly exported, working animation with invisibility won't work correctly if the hierarchy is incorrect.

I can't send it right now. Plus, I've already deleted the test files, and I would have to create them again. (This requires not only the animation but also a properly configured model. That is, the part you want to disappear must be a child of the bone for which you will create the disappearance animation.)

I advise you, if you have time, to just sit down and create a test dummy. A couple of cubes on bones.
The object's visibility is set here. In autokey mode, you can set different visibility for different keyframes. This way, the object will appear and disappear. For the bone to transmit its appearance/disappearance animation, the mesh must be a child of that bone in the scene hierarchy.


Added 2 minutes ago
If you manage to figure something out or do something, I urge you to share the information, just as I share it with you. And don't just throw a few phrases and then stay silent on the sidelines with a knowing look, saying "I know something useful, but I won't tell you," as you usually like to do.