Right now that isn't supported , the plugin uses a single encounter region ID, and each map has just one shared monster pool, so you can't split grass vs water encounters by region number on the same map yet. It's a great idea though, per-region encounter zones (region 1 = grass, region 2 = water, each with its own list) is something I'd like to add in a future update. Thanks for the suggestion!
I’ll write a devlog later once I’ve finished implementing your suggestions and ideas. Stay tuned!😁