One button somewhere or a key combination that works like Opera's Wand. This means, when pressing the button, the username and password on the current page are filled in automatically from stored password. I know that there is an option in chrome to display it automatically but sometimes for me it doesn't work.

Good idea, there is an extension for Firefox that is famous and does the same: Secure Login

make sure it works though because nothing is more frustrating then an almost working autofill

As I did post in another extensions topic, in Firefox there is something even more robust called "Sxipper" (the symbol is a dog). So when the page is loaded, Sxipper searches for all the profiles that were used in that page's form and provide a list. When you select one of the items, it autofills the whole form with that info.

And yes, Chrome is still kind of limited on that. It doesn't work so good with me too, sometimes it remembers and sometimes I need fill all again. This is a thing that I most missed from my migration from Firefox.