All Toolkit for YNAB settings and toggle state data is stored on your computer in your browser. We do not sync any data to the cloud.
Toolkit for YNAB sends errors to an external error tracking tool called Sentry (sentry.io). This allows us to react quickly to bugs that users are encountering without the need of bug reports.
Toolkit for YNAB will only run on https://app.ynab.com and https://app.youneedabudget.com which includes the application itself, the forums, and the login page. We will never collect password or bank account information. Toolkit for YNAB is completely open source which means the code can be read at any time in our GitHub repo to verify this.
The storage permission is asked for simply so that we can store both user settings and maintain state of toggles such as "Toggle Privacy" across reloads of the website.