Adding groups from a second source?

[Michael Carter]

Basically I want to setup employee hierarchy groups as there's some permissions we want to grant based on who they work for.

The hierarchy is stored in a DB table and it isn't possible to get it added to SAML/SSO as a "Group".   Been trying that route from 2020 to no avail.

Can someone point me at the extension points or libraries which I could potentially add "groups" from a second, and/or third source    (FYI: did looked at Role Based stragegy but for various reason we need to stick with "Project-based Matrix Authorization Strategy" so custom roles managed via script is out of the question)

Thanks.