what permissions are required for changing a Team Area membership relation or for changing the team area members

To change team area membership, you need the "Process -> Save_Team_Area(server) -> Modify_a_team_area -> Modify_the_collection_of_team_members" permission for one of the roles that you have in that team area.

I would like to suggest you open the a project area, go to the project area administration page and check the permission categories and browse for what they provide.

If you are new to the topic it might be a smart idea to read the help around it. E.g. https://jazz.net/help-dev/clm/index.jsp?topic=%2Fcom.ibm.jazz.platform.doc%2Ftopics%2Fc_permissions.html which would also provide you with the information you seek.

A simple third approach is to just try to add a member and save and carefully read what the error message is. That should direct you in which permission categories you need to read up.