cb privacy config

Hello and thank you for your answer.
I have already tried the solution you are talking about but it seems to me that this forces me to create a new tab display condition for each new author in the future.
I need something automatic.
For my solution I have one usergroup per author and only members affiliated with this usergroup can access the tab.
(eg "usergroup_a" users have access to the "author_a" tab, those of "usergroup_b" to the "author_b" tab, etc.)
Members can also be affiliated with several authors.
The value <Group_[cb: userdata field = "username" /]> calculates the right value (in this case "Group_author_a" or "Group_author_b" etc ...), so I need to find the value "Group_author_a", "Group_author_b" , "Group_author_c", etc ... in joomla usergroups.

I highly recommend you do not abuse ACL like that. It will grow exponentially and eventually cripple your site. That is not what ACL is for. If you want to assign User A to User B simply use an integer field for that. User B would have their fields value set to the user id of User A. This can then be easily conditioned against in CB Conditional, in CB Auto Actions, in IF substitutions and more without bloating ACL. There is no solution for what you're trying to do. ACL is checked against by their IDs not by their names.

ok i will follow your advice and use the conditional and privacy features of cb
I now note that the privacy config is correct in the backend but that it only appears partially in the frontend (only the public option is available)
What would be my mistake?

Then I see that the username does not appear in the wall and activity wall, what is my error?

I now note that the privacy config is correct in the backend but that it only appears partially in the frontend (only the public option is available)
What would be my mistake?

You've turned off privacy rules within CB Privacy > Parameters > Privacy > Rules.

Then I see that the username does not appear in the wall and activity wall, what is my error?

The field isn't accessible in that case. Ensure the formatname field is set to display on profile and is not being conditioned in any way in CB > Field Management. If you don't want it actually visible on profile you can move it to a tab that's in a not shown on profile position.

Then I see that the username does not appear in the wall and activity wall, what is my error?

You write : The field isn't accessible in that case. Ensure the formatname field is set to display on profile and is not being conditioned in any way in CB > Field Management. If you don't want it actually visible on profile you can move it to a tab that's in a not shown on profile position.

which fields should be displayed by default in the wall? formatname or username ?
(In my config both are visible in the profile, confidentiality : public, in general cb config formatname is set to "username only" )

formatname field is used to display the users name or username outside of profile. Access to username or the name fields doesn't matter in this case. You need to just ensure the formatname field is accessible. It should be set to display on profile, have no conditions, have no privacy controls. The same applies to the tab it is on. You can move it to a separate tab in a not shown on profile position if you don't want the field actually visible.