Just drag-and-drop a tab on the content area. A popup will be opened and you can choose the destination window.
The popup shows the previews of all windows. The one which has pink border is the current window and the one which has skyblue border is the destination window.

You can move a tab to another window from [Move to Another Window…] menu in the tab's context menu.

If you are using Multiple Tab Handler extension, you can move multiple tabs to another window at once.

To configure Tab Flick, go to [Tools] > [Add-ons], select [Tab Flick] and press [Options] button.