No, mine is capital M. But when you wrote you said you put it in mods.
Anyway, it should be
Mod
So, it seems you're correct. You don't get asked which mod to use when first creating a map.
When you go to create a map, you're only asked for the mood (day, sunset, etc).
What you can do is go ahead and save the map, and then when you go to open it in the editor again hold CTRL and it will let you re-select the mood and then let you choose the mod.