It could be useful for agent to support configuration parameter e.g. TLSPSKIdentityItem, with similar behaviour as HostnameItem, and in frontend possibility to opt for using the same string for PSK identity, as set for host name, on server/frontend side in host configuration.
Host name and PSK identity are both forced to be unique in whole ZABBIX, therefore it would be simplier to have the possibility use host name as PSK identity.
This would make also mass update of agent encryption simplier.
Changing host name on agent side without corresponding change on server side will cause agent unavailability, which is out-of-box detected and problem generated (in current state, just active items stop gathering data, what is less straightforward automatically detectable).