[wsng]

The regulation is enforced if someone uses it as title, e.g “Diplom-Ingenieur Max Mustermann”. I am not aware of a court ruling for any other kind of use.

That being said, in Germany there is no official degree named Diplom-Ingenieur Softwareentwicklung, it is always Diplom-Informatiker. Also, the Expression “Softwareingenieur” is not used, the straightforward translation of software engineer would be either Informatiker (emphasizing the degree) or Softwareentwickler (emphasizing the skill).

This is no legal advice: As far as I know, the regulation is strictly about German titles, so putting “software engineer” in your LinkedIn CV is out of scope of this law.