I found the culprit.
In the Opera Stable directory, there was the favourites database and journal. Those were created when I first installed Opera, after it went Turbo on me ... you know, ditched Presto for Chrome.
When that was created, there was a really poor bookmarks import utility available that would import all my Opera bookmarks and put it INTO the favourites. It created about 2000 bookmarks and many, many folders in folders in folders in folders.
Because I really do have a lot of bookmarks. I keep a lot of URLs handy that I sometimes do not need for years. 😉 Don't question it.
Anyway, these gazillions of bookmarks and subfolders IN the favourites, were causing this massive slowdown.
Now that I have all my bookmarks in the PERSONAL bar, I don't need'em down there anymore anyway.
🙂 So problem solved. The favourites routine just can't handle that much content.
Favourites = Quickdial