So the deck comes with difficulties when reporting bugs, but basically, you have to do the following.
- Go into Desktop mode
- Open the file browser
- at the bottom in the devices section, follow this path
- /Home/deck/.local/share/Steam/steamapps/compatdata/1371980/pfx/drive_c/users/steamuser/AppData/LocalLow/Moon Studios/NoRestForTheWicked/
There are your files.
To send them, do the same as PC, just on the deck. Remember, the Deck is a Linux system, so it functions like a Linux PC when in desktop mode.