Yes, you can make ahead potato salad and store it in the fridge in an airtight container. It is totally fine to boil the potatoes the day before and store them in the fridge as well as the sauce. However, if you want to serve a warm vegan potato salad, store the cooked, chopped potatoes separately from the sauce. The minute before serving, rewarm the potatoes in the microwave until lukewarm, pour the sauce, and serve immediately.