I used this to import a backlog of tickets from a CSV file.
You can customize the column headings & mappings pretty easily. This will not send any notices to your users.
You need to install https://github.com/helpscout/helpscout-api-php into libs/helpscout-api-php and initialize it with composer per instructions.
This is not for use as is and serves as an example for other users to start from.
Update config.php with your Helpscout API Key.
Look at uploads/example.csv for how the content was organized for this setup.