As I noted in my post, I don’t even have the Settings > Map > Markers section anymore after the latest update to 4.9.10. The entire markers section just disappeared from Settings.
Prior to the update, I was just using one of the default markers anyway, not a custom marker.
It is very likely I am missing something here, but this feels like a canned answer that isn’t taking my situation into account. If you need any sort of login access, let me know.