how do I find "delegated rights" assigned to Groups and Users

Hello,

I have been asked to manage a customer domain and document the rights/permissions assigned to users and groups. I could gather the information which are pretty straight forward such as Users in built in AD groups, group policy delegation etc...

AD is in good shape however the earlier admin left organisation without doing knowledge transfer. Lately I realised, he has a delegated rights to users and groups on some OUs and services which has been not documented anywhere.

Now my concern is, how do I identify what rights have been delegated to users and groups on AD ? I could not find anything upfront from AD UC.

Any help here would be really helpful.

Thanks