@leocg Thank you for your reply, but I've come to the conclusion that I asked the wrong question.
My question is: how can I go back to the old tab layout, independently of the tab islands? In the new tab layout, the tabs are so tightly packed that it's no longer possible to select one without error.

How to don't use Tabs Islands? I prefer the traditional presentation.
If it's not possible, then I won't use Opera anymore...