I did several tests to correct the error of the save file disappearing, but I knew that the save file of the entire user could be damaged.
So I worked on dividing the save file into several pieces.
For about a month or so, I went through a many R&D to support user mod.
But... I've never made scripting system for user mod in a game, so I still don't know what to do :s
I will study more about scripting system for user mod.
Instead, I'm trying to produce another sub-content.
I've only managed to organize my ideas now, so I think it's still too short to tell you.