Reimport Animation From Blender

So I have a model with a simple idle animation. When I added weapons to the model I went back to Blender to change the idle animation so that he is holding the weapons properly. I altered the animation, saved the file, then went to unity and clicked ‘reimport’ on the model. Only it still has the old animation. How can I add the new version of the animation?

Ideally I would like to do this without exporting the model from Blender, because I have multiple versions of the same model on screen and would be forced to replace each of them every time I need to add to or change the animations.

You need to have a prefab instance in the scene already in order to be able to apply changes.

Here is where the apply button for the prefabs is: