I think having the ability to save things you have created would be very beneficial. My suggestion for the game :)
An example would be that I just created a seven-segment display. It would be nice if I could copy it and save it to a list of some sort, and then I could go into another sandbox, and place it there without having to rebuild it from scratch.
Sometimes it is a little annoying, especially when I need to rebuild something such as a synchronous 4 bit counter and forget parts of it in the process.