Possible to edit sprite animations after creation, or create them from scratch?

I've created several sprite animations by dragging groups of sprites onto the scene area. However, is it possible for me to edit these (for example, to remove a frame, or to add a frame?) I've looked in the Inspector area for the animation, but none of the parameters there seem to have much to do with sprites.

In addition, I've noticed I can create a new animation resource manually, but I can't find a way to add sprites/frames to it. Is there a way I can manually add or remove frames?

(I'm using Unity 4.3) Thanks!