When I go to System->Administration->Users and Groups, that
should be listed
No, it shoudn't.
It is not.
When I do id new-user, it shows all the sssd information correctly and
the POSIX attributes that I set in LDAP server.
What do I need to do in order for the id new-user command information
to show up in the Users and Groups list on the LDAP client?
I know of no way to
make this happen. The tools you are referring to
just simply read the static /etc/passwd and /etc/group files. The ldap
client tools make the connection and request to the ldap server which
upon request hands them the credentials.
The tool id is completely different, as it runs through the pam setup
for user information which then directs the request to the ldap server.