You will be asked to provide the password you use to log in to Bitbucket every time you start Bittray.

It will not be stored.

The WCM is not a secure password store by default.

In order to securely store the password in the WCM (or registry, or anywhere) in a retrievable form, it would need to be encrypted using a passphrase provided by the user.

The user would need to enter that decryption passphrase every time Bittray launched to decrypt the stored Bitbucket credentials.

So you'd have to enter a password every time you launch anyway, saving no effort.

Storing it is arguably actively harmful.

So I just don't store it.