I agree, it's not only clunky, but a pain too. You' ll never see 'Save All Entered Data' by filling in fields. It's not a drop down or a pop-up. To access this feature click LP icon in your browser's tool bar, then click 'Add item' and then scroll all the way down to the last entry. There it is, waiting for you to use it properly. Finally, make sure that 'Automatically Fill Login Information' is enabled (LP icon>Account Options>Extension Preferences, under 'General').
PS. Never give up, don't allow the machine to defeat you.