Python preferences are available from menu Window/Preferences. Select item python.
A dialog box opens with two parts, a default directory for your script to record, and a python path part.

Record script in a preferred directory

If you want to record all your python script in a preferred directory, put the directory here. You still need to activate action Record script and to set a file name as described in section Tools/Record Script How?.

PYTHONPATH for fable GUI

You can add new python programs to fable python path in this preference: - Add zip/jar/egg - Add source folder