Add feature to play 2 designs at a time for more intricate patterns

The app updates have been terrific, especially being able to download tracks from the app.  Now everyone can easily do it.  I also love listing the drawing time.  If there is company coming over, I will choose a design whose write speed matches the socializing time.  I don't want visitors fascinated with the table but the track taking longer than their visit to complete.  Now I can plan one or more tracks to fill that time. If the talk slows down , watching the table never fails. 

Sometimes I play a track on top of the previous track.  Sometimes the double track is not any better, but sometimes it's twice as good.  Today I played the design AcklingDykeDorset after Fractal and the resulting drawn image was very beautiful and complex.  I am writing this one down to play again in  the future.  Other combinations, some planned but most by accident, often look really good , but I forget them.  I don't erase  often as I love playing open tracks on top of complex ones. My favorite designs overall have been these happy accidents.  It would be great if there was an option to save two tracks in a single action.