In some cases there are buildings with lots of similar rooms. To speed op the polygon process you can duplicate these rooms.
In this article we will learn two things:
After drawing the polygon press the S key on the toolbar or the Hot Key S. Press then the D button or hotkey. For each mouse click now another polygon will be created.
To edit a polygon first press the S button or hotkey, then press the polygon. Then press the M button or hotkey. The polygon will now get a blue square in each corner. Drag these corners to edit the polygon, you can also add additional blue squares for complex shapes.
Remember to press the save icon on the top right when finishing.