In social etiquette, when you leave the table during a meal, how should you put a napkin to show that the meal is not over and you will come back soon?
According to normal social dining (especially western food), if you leave the table halfway, you should fold your napkin and put it on your seat at will, which is a recognized indication that the meal is not over (not finished). If you leave it on the table at will, the waiter will easily pick up the unfinished food when no one is around, but it depends on where you eat.