connections created with wpa_supplicant are not used with iwd
After switching to iwd, some existing connections are not reused. I had to reenter the password. I've experimented with the connection files a bit. If I add:
wifi-security section in the original connection file then it is used again. This is a simple WPA2 AP.
No manual configuration was needed except entering the password, so it should be possible to just reuse the connection and add the necessary fields.