I guess I misunderstood. Sorry.
However, there is at least one plugin that provides an OR master key arrangement of a sort: KeePass-CertificateShortcutProvider. As described in the link, this allows unlocking your database with either a passphrase or a .cspkey file (Certificate Shortcut Provider Key).
However, there is at least one plugin that provides an OR master key arrangement: KeePass-CertificateShortcutProvider