I'd like to restart my progress since I haven't played this game in a long time.

Nvm, I used my scroll wheel and got this. 

For anyone asking the same question as me:

On Windows, it’s in Users/[Your Username]/%APPDATA%/Roaming/Wrangler/Player0.savefile

On Linux, it’s in ~/.local/share/Wrangler/Player0.savefile