How can I copy specific wifi networks from one Android device to another?

Question

I have a rooted Android 7.1.1 phone with a large number of wireless networks configured; some of these are relatively complicated (EAP-TTLS, custom CA certificate, whatnot; the point is it's more involved than just a shared secret).

I would like to copy some of these networks to another phone, also rooted (running reasonably recent LineageOS, likely Android 9 or 10), without overwriting other wifi configuration that exists on the destination phone.

I know I could use something like Titanium Backup (which I bought) to do a full backup of all wifi networks from the source phone and restore it on the destination phone, but that doesn't meet the following two needs:

1. don't transfer all, just some saved wifi networks;
2. don't overwrite existing networks on target device (just add new networks).

I'm also not certain it would correctly transfer the certificate along with the network it pertains to.

I looked at How to copy wireless networks list from one android device to another?, but that also only addresses copying all networks, not cherry-picking.

I suppose I could merge the new networks into wpa_supplicant.conf, but is that safe to edit while Android is running? Won't changes be overwritten? (Update: it would, unless editing while in recovery mode; see How to modify wpa_supplicant.conf) (Also, I'd still need to find a way to transfer the CA certificates.)