“加菜”常见的英文表达有 “order additional dishes” 或 “add more dishes”。
order additional dishes：更正式一些，常用于餐厅点餐场景，表达额外点菜、加菜的意思。例如：We decided to order additional dishes because everyone was still hungry.（我们决定再加些菜，因为大家还都没吃饱。）
add more dishes：相对更口语化、随意一些，同样表示增添更多菜品。例如：Let's add more dishes to make the meal more satisfying.（咱们再加些菜，让这顿饭更丰盛些。 ）