Substitute for Chinkiang vinager
In America's Test Kitchen's recipe for Hot and Sour Soup (sorry, paywalled), they call for 5 tablespoons black Chinese vinegar or 1 tablespoon red wine vinegar plus 1 tablespoon balsamic vinegar. So a 50/50 mix of both vinegars for more than twice the amount of Chinkiang vinegar. I have made Hot and Sour Soup with Chinkiang and with the red wine and balsamic substitution. I can vouch for the substitution.