You are correct: "Administrators can configure CA Identity Portal to manage two types of objects: users and groups" as discussed in Module - CA Identity Portal - 14.1 - CA Technologies Documentation under "Module".
"The user is the most fundamental entity in the CA Identity Portal application. The user entity is a representation of an organizational entity as it exists in the various IM/IG systems connected to CA Identity Portal.
The group entity has been introduced in CA Identity Portal version 1.5 and now allows the management of group objects as well. The group entity like the user entity is a representation of an organizational entity as it exists in the various IM/IG systems connected to CA Identity Portal.
CA Identity Portal does not save organizational users and groups' information. Instead, it fetches the information from the connected systems on demand."
Managed Objects - CA Identity Portal - 14.1 - CA Technologies Documentation
I am not aware of way to create modules to manage organizations. If the greater IMAG user community does not respond with further information on how this can be accomplished or a custom solution, you may consider expanding on the details of your use case and opening an IDEA on the community.