You can have your account and everything in it deleted at any time, and you do not need the app installed to ask.
Write to iamajavagod@gmail.com with the subject Delete account. Send it from the email address linked to your account, or include your username so we can find it. We confirm and delete within 30 days of the request, usually within a few days.
If your account is a guest account with no email address and no Google account linked to it, tell us the username shown on your profile — that is enough to find it.
Deletion is permanent. There is no way to restore an account afterwards, and the same email address can be used to sign up again from scratch.
Two things survive deletion, and neither contains your name, your content or any other personal data:
If you only want to stop using the app without deleting anything, sign out instead: Profile → the gear icon → Sign out. Your favourites and your arrangements stay as they are, and you can sign back in later.