How are your developers managing individual vaults for a given project outside of repository?

I see plenty of commentary on how Ansible vaults can be organized by inventories, however I haven’t heard how developer-specific vaults work for a given project as I wouldn’t want those checked in to SCM not to mention some of the things in said vault would be used in multiple projects. So anyone can anyone share what they do for supporting development vaults and how those are leveraged across projects?