When things go "according to plan," it means that they are unfolding as expected and predicted. There are several synonyms for this phrase that can be used interchangeably in different contexts. "As intended," "as envisioned," or "as scheduled" are all ways to express the idea of things going according to plan. "In keeping with expectations" is another phrase that conveys the same sentiment. "On track" and "on course" are more casual ways of saying that things are unfolding as they should. Using these synonyms can add variety and depth to your writing or speech, making your ideas more precise and well-articulated.