Had this issue last night, with the help Raliv himself, i have the answer for you.
"If you paste the following into your windows explorer, it will take you right to the data if you did a normal install:
%AppData%..\LocalLow\RalivDev\Archipelagates
from there, you can delete whatever you want to clear stuff. NPCs are saved in the npcs folder
appearances and saves can be deleted from in game."
-Raliv
DISCLAIMER: This only applies to NPCs YOU have made!