In Thunderbird 60 (Beta) Win-10 is the complete menu item text missing in "Tools" menu. Only the icon is visible at this menu item. In the "hamburger" menu is a complete empty menu item (no text and no icon) from this add-on. A click on the defect item(s) opens the saved logins dialog.
(EDIT: thanks for your understanding. I'll leave the below reply as is for other people's benefit.)
Yes, that's the point! As the description says, it's "made for applications other than Firefox". A single extension can no longer be compatible with Firefox and anything else at the same time, thanks to Mozilla's decision to support only WebExtensions on Firefox.
And no, there is no equivalent available for Firefox Quantum, and there won't be for at least a while. Currently, WebExtensions cannot access saved logins. Until Mozilla devs get around to fixing that, there's nothing I can do. Unfortunately, they are in no hurry about it, as someone started a project well over a year ago, but there is still nothing implemented in releases. You can see more about it at https://bugzilla.mozilla.org/show_bug.cgi?id=1324919
If you don't like this, you'll just need to work around it one way or another (for instance, go back to a pre-57 version, or switch to one of the forks like Pale Moon, which Classic Password Editor supports).
I'm happy to have this to replace the previous one being rendered obsolete by the changes in ffox. I know that having this handy icon for reviewing, updating and all aspects of password management is a life-saver for me and all my SeaMonkey-using clients. We love it.!