Thanks. Now that I looked into it again, the issue I have is not just the Duplicate Tab feature, but that opening a link in a new tab or window clears the history of that new tab/window instead of cloning the history of the source tab. that means that you can't quickly open a couple of links into new tabs/windows, with each of them preserving the current history. I don't think there's a fix for that.

Ah yes, I remember loving that feature in Netscape at the tail end, when it was just an altered clone of Firefox.

I got used to losing it eventually after switching over, but I do remember it being a painful transition for me too.