The option I found to upload/download syncs via Ren'Py sync server shows on the save/load screen. I used this method to continue my save from that website mentioned prior onto the downloadable client you provided here.
The site hosts a bunch of NSFW games, I just happened to stumble across yours on there and I love it, top to bottom. Great writing and excellent understanding of the verse and its character dynamics 🔥
Can't seem to attach an image today without getting an odd error, but the sync option is noticable underneath the save/load slots.