Only minimal subset of options, including security options, for SAML configuration can be configured via UI.
This leads to requirement to have write access to frontend server configuration file zabbix.conf.php.
Zabbix super administrator may not have such access and this will lead to inability to configure SAML authentication.
As there are many supported configuration options, it would be useful to identify the most critical ones and move them to "Users / Authentication / SAML settings".

Supported options listed on documentation page.