The mission of animators is to create nuanced, high-quality character motions. To achieve this, the careful editing of animation curves---curves that determine how a series of keyframed poses are interpolated over time---is an important task. Manual editing affords full and precise control, but requires tedious and nonintuitive trials and errors. Numerical optimization can automate such exploration; however, automatic solutions cannot always be perfect, and it is difficult for animators to control optimization owing to its black-box behavior. In this paper, we present a new framework called optimization-guided motion editing, which is aimed at maintaining a sense of full control while utilizing the power of optimization. We have designed interactions and developed a set of mathematical formulations to enable them. We discuss the framework's potential by demonstrating several usage scenarios with our proof-of-concept system, named OptiMo.