Celti [1] filed a deletion request for strongswan-networkmanager [2]:
strongswan's networkmanager support is quite broken right now with the
release of nm-1.2; further, this is just a slightly tweaked copy of
the strongswan package with the --enable-nm flag added. I stopped
using it ages ago and nobody's picked it up; it can go away.
[1] https://aur.archlinux.org/account/Celti/
[2] https://aur.archlinux.org/pkgbase/strongswan-networkmanager/