20.04 – Editing systemd config files – when do changes become effective?

I’m on Ubuntu 20.04. I’ve just edited /etc/systemd/sleep.conf to disable “suspend” mode. The UI’s “Settings” picked up the change after a short while, by no longer displaying suspend-related options.

Does that mean that systemd has also quickly noticed the change automatically, or is there something I have to do to make the changes effective? (I’ve checked the manpages, and nothing is mentioned about it).

If it’s automatic, is there somewhere that logs it? I’ve checked /var/log/syslog and journalctl -u systemd-suspend.service and there’s nothing obvious.