Ah the Eisenhower method of task management. I don't think the iCalendar standard Vivaldi implements here has some parameters for this, but only state and due date. I think the proposal is interesting so you get my vote, but I doubt this will be implemented. Just like I think my proposal to show a Kanban board to organize tasks won't ever see the light of day (which is essentially just another 2 dimensional sorting of tasks just like the Eisenhower you suggest)