Don´t remember where in user/appdata/local/slimjet/userdata/default (because I don´t use it now for problems in the login data in gmail) is the archive that you can delete to erase the passwords.
In settings passwords and forms untick use quickfil form filler .....
The archives with the passwords are in user/appdata/local/slimjet/userdata/default/forms with the extension .sbfm there you can delete them after unticking the use of quickfiller and closing slimjet.
Clearly I am not awake yet here as I repeated the same solution in my post above that was already posted as to where to turn things on or off in the settings. Oops.
You can toggle the use of Quickfill in Settings under Passwords and Forms
For those of you who wear aluminum foil hats, the voices lie, don't believe them!
Mostly my replies are about Windows OS. If not I try to remember to specify Linux.