I want to change title/description or add more variations during sales event


You are free to make any changes during sales event. Please go ahead and modify your listings. The only important thing is that sales event discount value must be applied to new price (including variations prices). In this way we can automatically calculate right price for newly added or changed variations after sales event is over so you won't need to modify it manually. 

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I liked how easy it is to create a sales event and how it displays in my shop. It is also very easy to schedule sales events.