Either list of just separated by some character to the current field.
Some times there are completely different URLs for same credentials. Like I have my Online banking and same credentials with totally different URL is used for authentication on some Government sites (Like tax and so on). Credentials are the same and the "account", but the URL is not. this would make much easier to administer the account, no need for multiple entries for each URL.
I could use the Browser override, but it would be difficult to remember which browser I need for which site.