SDI is the abbreviation for Single Document Interface.
In IBExpert this option has the effect that the windows are spread freely and somewhat haphazardly over the screen, similar to Delphi. The status bar is part of the upper menu and toolbar panel.
Careful: it is possible to accidentally move a window totally out of view!
When altering the user interface from SDI to MDI and vice versa, IBExpert needs to be restarted for the change to take effect.