Automatic reference to fields in other documents (APP)

I have meanwhile the whole documentation of users / groups and permissions in seperate Apps (App in a Minute) deposited.

In all apps, there are corresponding fields, for example, for users in which groups he is, for groups what authorization this has.

Under Group-APP there is also the field Members and here I want to have a program code automatically the users in it who have entered the same group in the User-APP.

So I am looking for a statement that says:
if the user has the group A in the field Group, then insert the user ID in the field Members of the Group-APP.

Is something like this possible.
Unfortunately my programming knowledge is not sufficient for this.
Could someone please help me here?

Thanks in advance

Don’t understand in full what your goal is, but are you aware of the “Admin Tools” App and the “Show Rights” page?

sorry that my explanations are not really clear…
It is not about an admin tool and the display of rights.
It is only about finding a way to automatically read and transfer data across applications (App in a Minute).

For example:
App1 User-DB
Username; User-ID; Mail; Group Member
Bodo example; Axxxx;; PDF-Admin

App2 Group-DB
Group name; description; Members
PDF-Admin; PDF-Admin Group; Axxxx

In the User-DB I have all users in it and if the user is a member of the group PDF-Admin which I can enter as a link, then the Group-DB should automatically contain the User-ID.

The question is if this is possible?

That has nothing todo with this xwiki User and rights it is just some documetation Pages written in APP in a Minute.

Thank’s for helping!

I see. I never used App in a Minute, so I can’t tell. However, technically this is possible with xWiki programming, I just difficult to maintain the string in the Group-DB, as you would need to parse and re-write it every time you add/delete a group with a user. Not sure how concurrency is handled in this case. Probably there is a very low risk for that.