I just dealt with this. I just searched for config.json in my APPDATA folder and it popped up. Dunno why I can't seem to actually find it even with hidden files shown otherwise, but it worked for me!
It doesn't actually exit the program when you close it, so if you try reopening it nothing seems to happen. Check your tray on the bottom right (if you're using Win10) there should be a little JRNL icon, you might have to press the ^ arrow icon to find it.
