If we get discounts on dining, it's all 20% right now. (Dining run by other companies can vary.) I haven't seen a list of 40% offers since before lockdown in 2020. I believe Sebastian's is on the list. You can find it on The Hub. They update it every so often with blockout dates and it also lists if certain meals are not discounted. For example, at some places you can get a discount at breakfast but not at dinner.
Also, if you haven't checked it out already, the Family Holiday Celebration includes dining coupons that can be used throughout the year. Some restaurants aren't included. Best to check the list on The Hub for those as well. I couldn't use mine at 'Ohana for example.