Symlink the file to the profile directory:
```
ln -s ~/.config/firefox/userjs         ~/.mozilla/firefox/[PROFILE]/user.js
ln -s ~/.config/firefox/userChrome.css ~/.mozilla/firefox/[PROFILE]/chrome/userChrome.css
ln -s ~/.config/firefox/userContent.css ~/.mozilla/firefox/[PROFILE]/chrome/userContent.css
```

Copy content of treestyletab into the editor within the addon settings window