We currently have only a shortcut to fill in a password. It would be great to have a feature to fill in a latest used identity too as well as card details. I use these a lot.
For identities, it could be cmd+shift+a ( as Address, because cmd+shift+i is used for mail client by default )
For cards, it could be cmd+shift+k ( as c is used to copy things )
Though default shortcuts does not matter much, because chrome allows to remap then easily.