Setting gamemode per world?

I have a personal modded server that I've been building out for family use. It has a hub island with portals setup with the portal world mod that warps to different worlds. The three main portals are Adventure, Creative and Creative flat. I found a mod called autogamemode that automatically switches the game mode to creative ONLY for a world named creative. I would like to have the default game mode for my flat world creative as well. Changing the game mode in the config for the world has no effect.

Is there any other way to force the game mode for a specific world?

When looking at the source code of the mod it seems it is hard coded to only change the game mode to creative if the world's name is creative. Would it be possible to edit the string to add more names? I have no experience coding so if there's anybody out there that could help me with this I would greatly appreciate it!