...manipulate Buttons in the OpenDialog's Toolbar?

uses
  CommCtrl;

// Beispiel: Blendet den Button zum Erzeugen eines neuen Verzeichnisses aus.
// Example: Hide the "Create New Folder" Button.

procedure TForm1.OpenPictureDialog1Show(Sender: TObject);
const
  TB_BTN_NEWFOLDER  = 40962;
var
   hWndToolbar, wnd: HWND;
   tbInfo: TTBButtonInfoA;
begin
    tbInfo.cbSize := SizeOf(TTBButtonInfo);
    tbInfo.dwMask := TBIF_STATE;
    tbinfo.fsState := TBSTATE_HIDDEN or TBSTATE_INDETERMINATE;

    hWndToolbar := FindWindowEx(GetParent((Sender as TOpenPictureDialog).Handle), 0,
      'ToolbarWindow32', nil);
    SendMessage(hWndToolbar, TB_SETBUTTONINFO, TB_BTN_NEWFOLDER  ,LParam(@tbinfo));
end;

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