We were migrating data from Help Scout to another service and Help Scout doesn't offer any 'Export' option out of the box. Instead, their MailBox API has to be used.
This project only supports exporting conversations + threads, as we needed only that, but extending it to other resources should be easy.
As the access token is a 'long-living' one (48h), I didn't implement token refresh.
The required flag is an access_token (at) acquired by invoking the Token (https://api.helpscout.net/v2/oauth2/token) API with either authorization_code or refresh_token grant.