As described in the tutorial, I was jumping backwards, inside “research” folder, with the back arrow.
After three clicks, the application crashed.
At launch, Inspector pane had been closed, and the settings in the “compile” box were changed : the not included files were marked included again.
I clicked on compile and noticed that the path was reset to the one I had been using while reading the tutorial : That was yesterday, right after installing. Many folders have been opened since.