Open page into a new windows

Here’s a practical use case:

I’m testing on one page and jotting down my observations on another. I’d like to be able to display them side by side for a smoother, uninterrupted workflow.

Tabs are useful in many situations, but in this case, I need the note-taking page to always be visible; and on the other hand, I need to be able to do whatever I want (browsing, creating pages, etc.) without getting lost when I want to quickly jot something down.