Upon opening a new tab it will sometimes get moved to a new window. Just now as a matter of fact I was opening 4 new tabs in succession. When I opened the final fourth one I clicked back to the main tab (#5) & immediately all following tabs were moved to a new window. Why does this sometimes happen & is any 1 else having the same problem???
You can detach a tab from the current window and open it in a new window by dragging a tab in the browser window.
You can drag that tab back to the tab bar in the original window to undo that detaching.