Evidently Opera 55 is buggy, because everything is slowed down, bookmarking normally is practically impossible, videos stop and start instead of running smoothly. The other 3 browsers that i use do not have problems like that. I am back to Opera 54, since that version works.
I do not use VPN. If I opened a second tab manually and then tried loading a page from a bookmark, I got nothing. If I tried opening another tab from a link in the index for this forum, it did not load. The only way I could get a new page to load was from the one tab I started with. I have given up on the latest Opera version and gone back to the previous one because the latest caused too many problems. It also seemed to want to preload pages from my bookmarks whether I wanted them or not. It also started out by disabling half of my extensions.
I found out that it was an experimental setting that caused the problem: "Redesigned bookmarks page
New design for bookmarks page supporting dark theme "
That is a misleading explanation. The dark theme only changes the colours, but not the function. Why anyone would want an interface like that is a complete mystery to me.
There is an experimental setting called "Redesigned bookmarks page" which is explained as being for the dark theme. That is what wrecked the bookmark manager interface. The dark theme with that setting makes no difference as to how it works. That just changes the colours. Why be so misleading about that setting?