[olbeup]

Código Delphi [-]
procedure TfrmPrincipal.ShowButtonVisible(btn: ShortInt);
begin
  Button1.Visible := (Button1.Tag = btn);
  Button2.Visible := (Button2.Tag = btn);
  Button3.Visible := (Button3.Tag = btn);
  Button4.Visible := (Button4.Tag = btn);
end;

procedure TfrmPrincipal.ShowTabSheetVisible(ts: ShortInt);
begin
  TabSheet1.Visible := (TabSheet1.Tag = ts);
  TabSheet2.Visible := (TabSheet2.Tag = ts);
  TabSheet3.Visible := (TabSheet3.Tag = ts);
  TabSheet4.Visible := (TabSheet4.Tag = ts);
end;

Sustituye éste

procedure TfrmPrincipal.dxBarLargeButton1Click(Sender: TObject);
begin
PestaniaVisible(0);
end;

Por éste

Código Delphi [-]
procedure TfrmPrincipal.dxBarLargeButton1Click(Sender: TObject);
begin
  ShowButtonVisible((Sender as TButton).Tag);
  ShowTabSheetVisible((Sender as TButton).Tag);
end;