Checkpoint64 has a preset for Big Walk: it already knows where the save folder is, backs it up automatically and keeps every version. Everything this site has on Big Walk:
Big Walk
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Save file location
Windows:
%USERPROFILE%\AppData\LocalLow\House House\Big Walk\user_data\save_games
macOS:~/Library/Application Support/House House/Big Walk/user_data/save_games
Linux:~/.var/app/com.valvesoftware.Steam/.local/share/Steam/steamapps/compatdata/1478500/pfx/drive_c/users/steamuser/AppData/LocalLow/House House/Big Walk/user_data/save_games -
Sharing with friends
How to share your Big Walk world with friends, from playing live to taking turns when the host is offline.