Adding new animation?

Say I import an fbx which has attached to it 2 animations: “idle” and “run”. and I make a character with it and do lots of stuff… then one day I realize I want to add “jump” animation. is it possible to just animate a jump in maya and somehow attach that onto my current character in unity? or do I have to import a new fbx and start over from scratch…?

Well, I found a solution. although its not the kind I hoped for, but it still works great.
if you read animation documentation, it mentions using @ to have attached animations. and all my meshes should be parented to an empty game obj, so i can update them whenever i want without messing up prefabs.