What is the name of save files? In the game's folder.
you have to check your AppData folders; check for the developer 'Scarlet Paper' folder, then you will find the gamesavefile00 or something, that is the actual save file you have to edit with 'www saveeditonline com'
remember to not stay in the first area in the game, use at least 2 portals, then close the game, upload the save file, edit it as you like (like gold, damage, speed movement, states, effects, locks etc...), download it and replace it in that folder, reopen the game and enjoy the edited save file. Keep in mind you'll have to re-do this editing when you complete the stage and defeat the boss.