I enter all my ingredients into a spreadsheet, multiplying ea. nutrient by the number of servings. (can of beans = 3.5 serv, so multiply info on label by 3.5.) I add up the totals & divide by the number of grams per serving, then enter that as a new food, adding the date to the name of the food.
I copy & paste my list of nutrients (calories, fat, sodium, carb, vitamins, etc.) into a new spreadsheet each time. I often use what I have when cooking, so I often pull up an old spreadsheet & replace ground turkey with cubed chicken, for example. I can edit the food in SP to make changes.