I did not mix anything.
The game is based on Electron, which has the same engine of Chrome. The F11 key may work or not, depending on the project settings: some devs disable it, some don't. I haven't tested this game.
As for the F12 key, I use it all the time with RPG Maker games: I just replace the exe shipped with the game and use the one from NW.js SDK. I would not be surprised if there was a similar trick with Electron too.
In the saves you have shared, they are stored in "Local Storage\levelbd\0000.14.lbd" (the number may change with the user).
Editing the file with a HEX editor is not for everybody, that's why I thought of launching the dev console.:
Code:
>localStorage.Settings
"{"Language":"English","Volume":{"Music":"1","Voice":"1","Sound":"1"},"Resolution":"960x540","TextSpeed":20,"AutoPlaySpeed":55}"