There's no way to configure libreswan VPN from the plasma-nm editor. It would be nice to have an interface for it, some distributions like Fedora Linux have switched from openswan to libreswan.
The plasma-nm openswan VPN frontend was renamed to libreswan with plasma-nm version 5.24.90. https://invent.kde.org/plasma/plasma-nm/-/commit/261298a06908de2f4c2b121ba1e0d1d29a25d6a0