At the URL opera://activity, I'm not sure why the sessions from the other device are not showing so that you can go into one and manually open each tab in the current Opera. However, in one Opera, you can right-click a tab, goto "save" and choose "all tabs to a speed dial folder". Then, in the other Opera, goto the URL opera://bookmarks, go into the "other speed dials" folder, find the speed dial folder for the other device, right-click it and choose "open all in tabs" to open them all in the current Opera. That's assuming you're syncing bookmarks of course. You can then delete that speed dial folder of tabs if you want and empty the bookmarks trash.