Has anyone ever cooked with hyssop?

Yes. I have used it once in making za'atar blend.
That in turn is used on baked potato, salad vegetable and meat roasts etc.
Had high hopes for the hyssop but found my particular batch low in flavor. For later batches of za'atar, I replaced it with thyme, savory or oregano. Hope yours has more taste.

Hyssop has a mild liquorice flavour and is usually used as a tea. I grow it in my garden and usually add it to salads or to flavour iced tea or garnish cocktails. I have never cooked with it.