Hi,

1. I would build a smoke prefab.
2. place the prefab on the image to get koordinates and size
3. spawn it current runtime

is that a good plan, is there a better one ?

Yes, that is a good plan! I highly recommend joining our Discord and registering your copy so get to download the pre-release v1.16 which introduced a way to set spawned object's position in naniscript. You can find more information here: https://naninovel.com/support/#naninovel-support

Cool, thank you