What is the ruling on supplicating with the words: "O Allah, grant me the things I don't know how to ask You for, for You know best what my soul desires"?

We are unaware of any impediment that would prevent supplicating with the wording mentioned in the question, as long as it does not involve aggression or sin. However, it is more preferable to choose the reported (from the Prophet) wordings, as they are superior and more conducive to a response.