I want to create an event when a dataset is successfully submitted (such as feedback) but not if it fails. How do I create this event?
If you mean an event that is fired after an item was saved into a collection, then you can try onAfterSave() for your dataset.
You can find more information about it here: https://www.wix.com/corvid/reference/wix-dataset.Dataset.html#onAfterSave