Unfortunately, no. Reloading certificates and configuration requires a full restart.
There are a handful of neo4j dynamic configuration options that can be changed while the server runs, but many system-critical ones are not included in the dynamic set.
This topic came up again as we're looking at clustering Neo4j 4.1.1 - from reading the updated article:
do we need to actually restart the database or is the certificate periodically reloaded without us restarting neo4j's systemd process? Such that all the cronjob or other orchestrator needs to do is update the certificate?
I'm assuming that you still need to bounce the server to get the new certs in.
If this is a cluster, you can bounce one server with systemd at a time, and not cause a complete outage. This is also how you would upgrade neo4j without the cluster being unavailable. See: https://neo4j.com/docs/operations-manual/4.0/upgrade/causal-cluster/#cc-upgrade-rolling