Currently the FMGUtils class has a hardcoded filename used when reloading the FMG files. This fails when I load my renamed .fmg files, breaking the Import Map button.
This appears to be the line that causes the issue.
ItemFMG = FMG.Read(fmgBnd.Files.Find(x => Path.GetFileName(x.Name) == "アイテム名.fmg").Bytes);