Thanks to intense use of the internet I finally found a simple, understandable way of implementing Save and Fetch operations, enabling the keeping and reusing of any construction.
Here is a reminder of the application (app, program, software, whatever), with the file handling operations:
There is now a not quite finished Spanish option – just click “ESPANOL”
Also a modified “move object” procedure for use with a tablet,or even a smartphone.
The whole application is constructed as a web page, and to run it just click this link: geostruct