For tarragon vinegar, you can substitute either fresh or dried tarragon plus vinegar in a recipe. Use a tablespoon of fresh tarragon leaves to a cup of vinegar or a teaspoon of dried tarragon to a cup of vinegar.
White wine or champagne vinegar are best for this substitution. You can also make your own tarragon vinegar by steeping tarragon leaves in white wine vinegar. Warm up the vinegar before adding the leaves. Shake vigorously, and then seal the container for several days. Make sure to change out the leaves once a month or so. You can also use apple cider vinegar in this application.