The "Directory Managers" group in LDAP was inherited from OpenDJ. It grants full write access to OpenLDAP via ACLs (in addition to the cn=admin user).
It's however a different group type compared to all other groups in LDAP (groupOfUniqueNames as compared to the default groupOfNames). Thus the membership attribute is also different. For consistency it would be nice to only deal with one group type.
The group currently contains two members from Ops and two system users: uid=novaadmin and cn=scriptuser. It needs to be checked which of those actually still use the group, if only cn=scriptuser remains we could just as well drop the group and add this to the ACLs directly.
If cn=admin is insufficient, OpenLDAP could also be configured to accept a root-accessible ldapi socket for simple Ops access.