SSID - Client MAC Address Filtering - LOCAL not available

Hello Community, 

we have a FortiGate 200E (6.4.5) and any WiFi-APs (231F). We create a SSID for "Guests" (all fine) and a SSID for "Internal". We like enable "LOCAL MAC Address Filtering" for "Internal", but the option is over the web interface not available.

Over the CLI it works! (https://docs.fortinet.com/document/fortiap/6.4.0/fortiwifi-and-fortiap-cookbook/512025/configuring-mac-filter-on-ssid) 

We want to maintain the MAC addresses permanently, but not via the CLI.

What can we do so that "LOCAL" appears in the SSID settings under "Client MAC Address Filtering"? 

Cheers from Germany