I want the ability to add a third line to the user/password section

Some websites requires the registration of a username, password and an email address.
Sometime it is not clear which one will be used as a login, and sometimes which one you
use may depend on context. 

I find it annoying to look for the field in the section beneath the Url
Though it is possible to (misuse) the Url field by adding a website
and using that to store the username

I want a 
Field1
Field2
Password

or
Field1
Password
Field2

All that is required is the ability to add an optional line to the user/password section.