You CTRL-select the tabs you want to move, then right click on them and then in the context menu that appears you choose 'Move selected tabs to new window'. This works for me, anyway.
Thanks, I've already found that out.. So, it all works only in sidebar? Actually it's not super convenient because it's not really easy to drag outside the edges and after you moved some tabs all windows that were collapsed are expanded again.. And if you want to drag more - you must collapse them again. And also it would be great if it (selecting and moving) worked in tabs bar. Is it even possible in Opera? Also, selection should work like in windows so if you hold Shift and click on some element, you should select all elements starting from current element. Because of that I've missed 100 times already and will miss million times again.. P.S. despite these conveniences this extension is great, helps very essentially for me as I open pretty many windows and tabs..