I think you are talking about the behavior as intended. To disable switching between recent tabs, disable "Cycle tabs in most recently used order" option in settings.
As a side note, this feature is one of my top-needed ones. You may also find it useful. Just hold Ctrl button as you tap Tab button and you'll see.
@mist7 Thanks for your answer, the problem is easy to explain: when I click on the floating button to separate nothing happens (no messages, no errors).
It's important to mention that I have been using Opera GX since it came out, and everything worked perfect. From the beginning I installed all the extensions I use regularly, since then I have not added any extensions.
Simply that function stopped working, maybe it's an update problem, I don't know.
I really love that function, in fact I would like to have the option to activate it by default.