You can create such section it via Layouts for the product page: https://take.ms/KwUfw
Or you can create such content in the HTML Block and then define it in Theme Settings -> Single product -> Add to cart and define that block in the “Content” area: https://take.ms/BYLMa
It depends on the conditions that was settled for product layout or in theme settings, if you use default conditions then it will be settled globally, so please clarify which method you use for showing such a block on the product page and I will explain how to apply it for certain products.
You can create a preset in Theme Settings -> Settings Preset with the condition that is related to the category: https://take.ms/dhpaM, then edit its settings and navigate to Single product -> Add to cart and define your created HTML BLock e.g in the Before “Add to cart button” area: https://take.ms/YzzU3 , thus that coupon HTML Block will appear on the specific category that we mentioned in our condition.