Add a Replace Bookmark action the the OnLeaveSheet trigger of sheet1 to store the current selections. And also add an Activate Bookmark action to the OnActivateSheet trigger of sheet1 to restore the selections from the bookmark. Use the same bookmark id for both these actions. You can add a Clear All action to the OnActivateSheet trigger of sheet2 (or add it after the Replace Bookmark action to the OnLeaveSheet trigger of sheet1). See here for an example.