Your conscientiousness is praiseworthy. However, despite your sensitivity, there are no grounds in Halacha to insist on differentiating between Shabbos and Yom Tov. If for practical reasons you choose not to cook on Yom Tov, this is perfectly acceptable. In fact, while prior to the days of refrigeration the only way to have fresh food on the second day of Yom Tov was to cook on the Chag, today many families find it adds to the Simchas Yom Tov of the wife to not have to spend hours of her Yom Tov slaving in a hot kitchen.
If, nevertheless, you wish to find a way of distinguishing between Shabbos and Yom Tov, a solution can be found with an electric hot plate. On Yom Tov you can place food directly from the fridge on this warmer, while on Shabbos it would not be done.