I don't see any way to "make unique" or similar in AnimationPlayer. and thus editing animations in inherited scenes also changes it in the base scene and is therefore useless.
I'm currently working around it by attaching a script to the AnimationPlayer and exporting a var for each animation and then putting a bunch of if isinstancevalid: add_animation for each one in the _ready function, but it doesn't seem like the ideal solution. It requires manually saving each animation individually and it doesn't update as responsively in the editor and etc