When you check the replay checkbox, the settings gets remembered during this session, even when starting a new map.
However after a restart this setting is lost again .
PS: I love the replay functionality! Please keep supporting it.
The map exchange string stores the options you've set for a map, right? But if I set all options to my heart's content, and also check the "Replay" option, then export the map exchange string, Replay won't be checked if I start a new game and import that same map exchange string.
A good mod deserves a good changelog. Here's a tutorial (WIP) about Factorio's way too strict changelog syntax!