Not that I know of - part of the piece it generates is the issue or merge request number and title, followed by a 5 alphanumeric character blob - perhaps a hash or randomly generated to avoid collisions.
even though these throwaway subdomains I generated are no longer accessible, it still has to remember it and sign OCSP for the next 3 months? Now I feel bad...think in the process of setting this cluster up over the last few weeks I generated and subsequently lost or deleted dozens of certificates as I tore down the cluster and remade it several times