Aggelos Karalias, one of the attendees at NetBeans Day Greece, has made a brilliant plugin for NetBeans IDE that provides code completion for Spring Boot configuration properties, click to enlarge the screenshot below:
Congrats, Aggelos! (And great to have met you in Greece!) As you can see above, it works perfectly.
I checked out the sources here, built, and installed them:
And then I used this project by Michael Simons, to make the screenshot above:
Also, this article is useful about Spring Boot and NetBeans, as well as other technologies, such as AngularJS: