I did away with Secure Logon a while back. There was a long dry spell between updates and it was starting to fail on some site it previously worked on. I emailed the apparently new maintainers Abine, Inc. and received this response:
Sadly we no longer provide support for these products. At this point the best I can do is direct you to these two pages for support:
If you have any further questions or comments or need additional assistance, please feel free to email us back at firstname.lastname@example.org (mailto:email@example.com).
I see there was an update on November 25, 2012, that response was November 29, 2012. (shrug)
The Secure Logon Add-ons page is basically an advertisement for DoNotTrackMe. (My opinion)
That doesn't answer your question though.
Create a bookmark called Remember Password (or what ever you like), then paste that code in to the Location block of the bookmark. When you are on a site that does not save your password, open your Bookmarks and select Remember Password, then try logging in again and see if it prompt to save. Like I said it does not alway work.
Another option is to install Saved Password Editor (https://addons.mozilla.org/en-US/firefox/addon/saved-password-editor/). This extension lets you add new logins and edit existing ones. Pretty handy.
Then there is QuickPasswords (https://addons.mozilla.org/en-US/firefox/addon/quickpasswords/). I am using this instead of Secure Logons, as I don't have much faith in Abine, Inc.
I really don't miss Secure Logon that much.--
Living in Paradise!!