Open tabs lost
An observation: if there are multiple windows open, Vivaldi will save open tabs...unless one of the open windows has all of its tabs closed, in which case upon next open the open tabs in the non-empty window will be lost. Or at least i think this is what's happening. Have had a number of important sessions lost because I failed to pre-close the no-tabs window before closing the main window. Continuing to love Vivaldi in general however.