Open Session on a new window
If I do Ctrl + N to open a new window and do Open Saved Sessions in it, it does not open the tabs on that new window. It seems Vivaldi tends to open the tabs at the very first window opened.
I guess that's more of an undeveloped feature than a bug, but I would expect a session to open in the current window. Maybe it just needs an option for "Insert Session," like in Opera 12.17?