To add a script you'll need to use the following command line options (with the values changed to match your requirements of course;)
-config script.scripts.name="Remove Strict-Transport-Security"
-config script.scripts.engine="Mozilla Zest"
-config script.scripts.type=proxy
-config script.scripts.enabled=true
-config script.scripts.file="/home/user/scripts/Remove Strict-Transport-Security.zst"
See also the FAQ: How do you find out what key to use to set a config value on the command line?