The app doesn't collect any personal data without your explicit consent.
On the "Skip waiting" screen, entered Steam id is used to verify that Steam profile nickname is in the correct format by requesting the profile from steamcommunity.com. You can enable "Remember my Steam id" switch to avoid entering it next time. In this case entered Steam id will be stored locally and used to prefill the text field.
If you send a support request (Settings -> Support) and leave your e-mail in the text, it can be used to get back to you regarding your request.