You may not see the Corporate Relationships Tab. When trying to create a subsidiary relationship between two organizations, you may not see the corporate relationships to see it.
Our Product Development team has reviewed this issue, its impact in the software, and the availability of an alternative solution. After careful consideration, we have determined that this issue will not be addressed currently in the Altru software. Product Development will be focusing development resources in other existing areas of the product, as well as new feature development.