You can access the configuration file going into Parsec's settings, scrolling to the bottom and clicking "edit the configuration file directly". These are available on all platforms, except Android.
Alternatively, you can find config.txt on your system's files:
- Windows:
- Per User installation:
%appdata%\Parsec\config.txt - Shared installation:
%programdata%\Parsec\config.txt
- Per User installation:
- macOS / Linux / Raspberry Pi:
~/.parsec/config.txt
You can see a list of the available configuration files here.