Open browser? Open new Window? Open new tab?
Are you opening/launching multiple browsers (e.g., Opera). How are you using windows? How are you using tabs?
If you have multiple windows open in one instance of Opera then closing that instance will close all of the open windows.
If I understand correctly you will need to have multiple instances of Opera open with only one window per instance.
That way you can close any given window/instance while the others remain open.
Additional explanation needed.
I just wish, when I launch Opera I can pick up where I left with my previous session. That being, with multiple tabs in multiple (at least 2) windows.
I can do that in Chrome & Firefox but not Opera.
I use Firefox for everyday & games, Chrome for school only, Edge for Netflix,HBO etc only.
I would like to use Opera for games only, it takes up a lot of space &time meddling around with it in Firefox.
My AD(H)D requires separation, so I don't procrastinate or get distracted.