It should be a standalone window setting.
Keeping the current progress shouldn't that hard since GG does something seemed with the checkpoint system, although it is not implemented in GG standalone.
Also, there is something to take care of as well, I'm going to explain to you all to get my point.
I have a Z lotion, if you own it and use it, you will be able to walk with the zombies without getting hurt, although it has duration time, if the effect finishes and you aren't done, you (the player) die.
Ok, the player dies, however still has 2 lives, so try 2, start to try 2, and man, the Z lotion is no longer there, therefore the player doe not have the z lotion, therefore he is unable to walk with the zombies, therefore the game end, because the engine does not reset all the level and start from scratch, so the player will have a second chance to try to.

Laptop: Lenovo - Intel(R) Celeron(R) CPU 1005M @ 1.90GHz
OS: Windows 10 (64) - Ram: 4 gb - Hd: 283 gb - Video card: Intel(R) HD Graphics
cpu mark: 10396.6
2d graphics mark: 947.9
3d graphics mark: 8310.9
memory mark 2584.8
Disk mark: 1146.3
Passmark rating: 3662.4