systemctl edit for own unit files in /usr/local/lib/systemd/system

Hi *, I keep my own systemd unit files in /usr/local/lib/systemd/system. Enabling them creates a link from the unit file in this directory to for example multiuser.target.wants. But editing them with systemctl edit --full and writing back the edited file creates a new file with the modified contents in /etc/system/system and leaves my file in /usr/local/lib/systemd/system untouched. So I have two files with different contents from now on, which is at least confusing. Is that really the intended behaviour of systemctl edit? Or am I doing something wrong? TIA. Bye. Michael.