Override this method when you need to switch managers. 

Application: 

There are several groups of designers (edited objects) with own component palette state and design objects. 

Usage: 

For each group there should be created own instance of TDesignManager (derived class). 

Derive new class from TDesignManager and override SetActiveDesigner. 

In SetActiveDesigner you should detect in which group this active designer is included and change DsnManager global variable. 

procedure TMyDesignManager.SetActiveDesigner(const Value: IDesigner);
var Mng: TMyDesignManager;
begin
  // GetManagerForDesigner - your function which detects particular group
  Mng := GetManagerForDesigner(Value);
  if Mng <> Self then
    begin
      DsnManager := Mng;
      Mng.SetActiveDesigner(Value);
    end else
      inherited;
end;

TDesignerManager Methods