TLDR:
When SNMPv3 settings are changed, snmp cache has to be reloaded with

zabbix_proxy -R snmp_cache_reload

Is it possible for Zabbix server to automatically pass config change to the relevant Zabbix proxy when necessary?

"We are currently starting to connect more and more Mgmt. systems like CISCO DNA Center or ARISTA Cloud Vision to Zabbix. This means that we not only automatically receive the information/alarms from the Central Mgmt. but also the SNMP access data automatically. This means that in the end we would have to build a cronejob or a script that is used for SNMPv3 access data every time a change is received in Zabbix from another system, also clear the cache on the correct proxy. From my point of view this is the wrong approach.

In the end I only see a solution here that the Zabbix server reports this information as a config change to the Zabbix proxy by changing the SNMPv3 access data in the database and this then empties the cache for exactly the necessary systems on the proxy.
The workaround via cli means that I always empty the entire cache for proxy.
We will now see how we can implement the workaround.
It would be great if such important functions were implemented in v7 or v8 for security reasons, as you mentioned, SNMPv3 data is also changing more and more. Some of our customers this happens once a year."