This is how I test the editor: Open status screen of a character, tab out, change STR for example to 333. Then tab back in, leave status and reopen status it shows 333. Then I save the game and close the game. Then I start the game again and load the saved game and it still shows 333.
In which case does it reset for you?
Ah, that might be the reason.
In my case, I open the status screen for a character, tab to the trainer/editor (I play windowed), edit the stat, tab back and confirm that it's changed. Then I leave status screen and open it back up, and it's still changed. Then I save the game, but I don't exit and re-enter.
I tested it after a battle earlier, and it had stayed the same, but when I moved to a new screen, it had changed back.