TMSFMXNativeUINavigationController1.PushViewController(Form3.TMSFMXNativeUIViewController1,true);

procedure TForm1.InitializeControl(AControl: TControl);
var
  I: Integer;
begin
  if not Assigned(AControl) then
    Exit;

  if AControl is TTMSFMXNativeUIBaseControl then
  begin
    (AControl as TTMSFMXNativeUIBaseControl).Initialize;
    for I := 0 to AControl.ControlsCount - 1 do
      InitializeControl(AControl.Controls[I]);
  end;
end;

procedure TForm1.TMSFMXNativeUIButton1Click(Sender: TObject);
begin
  InitializeControl(SecondaryForm.TMSFMXNativeUIViewController1);
  TMSFMXNativeUINavigationController1.PushViewController(SecondaryForm.TMSFMXNativeUIViewController1,true);
end;