This Horcrux password is new to me, so did I get it right, you'll have your password auto-filled by 1password (or whatever) and then typo your addition to it (which was stored in your head)?
I use the following at the moment: 1Password (Master pass only in my head, very long and random) All passwords generated and unique 2FA for all-important apps with G2FA
To me, that seemed pretty solid because even if you'd get my 1Password you couldn't really get into the important part.
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