Yes, you can add foods/meals that you already had by making updates to the Time of Food selector in Libre Assist* at any time. However, you are not able to add foods/meals that are in the future.
*Libre Assist is a feature within Libre app that uses generative artificial intelligence to provide information on how foods could impact your glucose levels. Generative artificial intelligence may not always be accurate, and it should not be used to make treatment decisions.