As of 7.0.0, there is the server runtime control option:

proxy_config_cache_reload[=target] Reload proxy configuration cache.

This does not however trigger a full config sync but just the normal incremental config sync, which means an empty response if there haven't been config changes.

As evidenced by ZBX-24658 (a serious problem where proxy forgets the host-proxy mappings in the proxy group and needs a full config refresh to be able to respond correctly again), there are cases where it may be beneficial to be able to remotely trigger full config sync for a proxy or for all proxies in Zabbix level (instead of restarting the proxy process in the OS level).

I'm suggesting adding something like "proxy_config_cache_full_reload" runtime control option that would force a full config sync.