The main idea wraps around the save file generated by the game. Let's suppose at one point you would like to go backwards just to fight one boss again without having to create a new save file, or you have just one sugar left, for example say you want use that sugar during the boss fight, but what if you didn't kill him from the first attempt? What if you died and besides that you lost your precious consumable, that's when this program becomes really useful. You could just make a save file before the boss fight where you have the consumable and if you die you would just load the save file.
The way it works is quite simple as long as you're aware of some things.
For example once downloaded the program it is going to ask you to pick up the actual save file from %APPDATA% and it's going to store that location in the config.terkea file
Then the actual interface will load, where you can create, load and delete save files.
The create new save file option is not related to the path from where you run the program. Which means that if at one point you decide to change the location of the program your savefiles are safe.
The way it works: It copies the savefile from %APPDATA% to the saves/savename folder. Also the name has to be unique in order to use it as identifier.
The same principle is used in the loading save file, it copies the savefile to the Sekiro %APPDATA% location.
Delete it's just delete, it permanently deletes the savefile and the entry from table view.