You may have to set up some custom fields. I believe that you will need two custom fields, and it seems that one of the custom fields should be configured as a “linked” field, given the name identifierId, and be linked to your Username.
I don’t have a Google login myself, so I can’t determine what the best setup would be for the second field (to correct the auto-filling of your password). However, the linked instructions explain how to find the custom field name that you would need to use for the password.
Looking at the HTML code, I’m speculating that it may be possible to define a second custom field named hiddenPassword, which would be linked to your Password.
Let us know what happens when you try this.