Thank you for contributing to the project.
Your comment revealed an error in the export script. In order to see the script in the blender export menu, the first line must be !BPY. If you look at the original script as posted, the first line is: import blender. The fix is to move this line down after !BPY.
As for why your animation did not show up in the game, it is hard to say. One thing I have not tried is replacing a game animation file entirely. The old anm file is always there in the PAK file and if for any reason the program does not find your file, it defaults back to the original. A lot of things can go wrong. If you have not already done so, you should familiarize yourself with flmreaderzero and create a new scene with your animation in it. This program allows you to swap out animations and view the results in the game. A good place to learn about flmreaderzero is here.
The tools in the package allow you to make a copy of an anm file and change the rotation data, and that is all.
To use your new animation, you need to create a new scene, create a new version of the *.flm file and edit it to reference your new animation. I would recommend that you give your new anm file a unique name.
My experience has been that it is best to take very small steps. First create a new scene with a new name, but do not change it. Once you get it to work, then change the flm file to reference your new animation. Please let me know how you are doing.
Thanks again for participating.