We already have TASVS-STORAGE-1.1 for secrets in binaries and configuration files shipped to users, and I think we could add another item for secrets in source code under TASVS-CODE. This is what we have in the ASVS under V6.4 Secret Management:
Verify that a secrets management solution such as a key vault is used to securely create, store, control access to and destroy secrets.
We already have TASVS-STORAGE-1.1 for secrets in binaries and configuration files shipped to users, and I think we could add another item for secrets in source code under TASVS-CODE. This is what we have in the ASVS under V6.4 Secret Management: