Adding Diary Categories

Is it possible to modify the Diary Categories, and only affect the current day and the future? I tried adding snacks after breakfast and lunch and eliminating the snack that is default after dinner. Unfortunately it changed all my previous days entries, so I changed back to the default. Would it be possible to give us the option of only changing future entries, such as when you modify a recipe? When modifying a recipe, you get a pop-up asking if you want to update previous entries.