List Google app script projects

I'm trying to list all my google script files using the Google Drive File API as documented here. However I always get back an empty [] list. I think my token and my scopes are fine as I'm getting back this from Google OAuth2:

{ "access_token": "xxxxx", "expires_in": 3600, "refresh_token": "yyyyy",
"scope": "https://www.googleapis.com/auth/drive.scripts https://www.googleapis.com/auth/drive.appdata https://www.googleapis.com/auth/drive",
"token_type": "Bearer"
}

But then when I issue the query using mimeType filtering (I just want to get google app scripts list):

mimeType = 'application/vnd.google-apps.script'

I'm only getting back an empty items list ([]), even if I've just created a google script inside a Google Sheet:

{ "kind": "drive#fileList", "etag": "....", "selfLink": "https://www.googleapis.com/drive/v2/files?q=mimeType+%3D+'application/vnd.google-apps.script'", "incompleteSearch": false, "items": []}

I'm guessing that app-script means something else than google script code which is part of a Google Sheet... Any help appreciated :)

About retrieving the file list of projects of the container-bound script type and exporting each script from the project, please check the following answer.

Retrieve file list of projects of container-bound script type

• Unfortunately, the file list of projects of the container-bound script type cannot be retrieved yet, while the file list of projects of the standalone type can be retrieved using drive.files.list of Drive API.
  • This has been reported as a future request. https://issuetracker.google.com/issues/111149037

Export scripts in a project

• When you want to export each script from a project of the containter-bound script type and the standalone type, you can do it using Google Apps Script API.
  • This might become a GAS sample script for your situation. here.
  • Also you can do it using a GAS library like this.