I do more or less what the OP does. I know it’s not safe, but there are simply too many of them for me to remember.
(We’re always advised not to use the same passwords for different accounts.)
Also, I need a versatile mnemonic file: simply having the login name and password isn’t enough. I need notes on sub-accounts, account numbers, group memberships, file paths, login options, etc. It’s convenient – but not safe – to have all of these in one big file.
Alas, I don’t really believe in the notion of a “hidden area” on the computer. I suppose I could jam it all on a USB memory stick, and simply unplug it when not in use.
I did use an encrypted password manager for a while, but it got too damn intrusive. It would pop-up at weird times, and would try to auto-fill information boxes that had nothing to do with my actual login. For instance, every single time I’d go to Amazon.com’s home page, it would try to fill in “my account.” Much too irritating!