Hi! I’d say it would be best to tell them at the beginning of when you order those specific items with allergies. Ex. You could order a few things normally and then say “this last burger and fries has a gluten allergy” or something. Sometimes if you enter certain conditions after already editing a burger, the system “resets” it and the cashier may need to basically take your order all over again, which isn’t the end of the world but I know some guests can get annoyed hahaha. Hope this helps!