Add Corners from scratch:
Get corners from processing and edit them in results after
Select either ‘Floor Plan’ or ‘Other’ type option in Properties panel of Takeoff Zone
In Processing Confirmation dialog, Corners item can be checked on for the Takeoff Zone while Walls, Windows and/or Rooms are checked on. If none of them is checked on, Corners can’t be detected and so the item gets disabled
After the processing, detected Corners appear in the Left Panel and in the Viewer: default shape is circle and default color is blue